Basics. Substitution with So, Not, and Do
Substitution with So, Not, and Do
Instead of repeating entire clauses or verb phrases, advanced English speakers use substitution to keep their sentences concise and natural. For example, rather than replying "I think she will win," you can simply say "I think so." Similarly, to express a negative expectation, you might say "I hope not" instead of "I hope she does not win."
This challenge explores the nuanced rules of clause substitution and ellipsis. You will practice negative transfer with mental verbs (knowing when to use "I suspect not" versus "I don't think so"), adjective substitution (like using "remain so"), and verb phrase fronting ("and so I did" vs. "I did so"). You will also navigate tricky distinctions involving stative verbs with "do" and the correct usage of "say" vs. "tell" with "so."
You'll work through 10 questions featuring a mix of single-choice, multi-choice, drop-down, and drag-and-drop formats.
Try the quiz to check your knowledge!
Adjective
Adjective vs adverb: both describe things, but adjectives attach to nouns while adverbs attach to verbs. A quick answer (adjective → noun) vs answered quickly (adverb → verb).
An adjective modifies a noun or pronoun — telling you what kind, which one, or how many: a red car, something useful, three heavy boxes.
Diagnostic test: if the word describes a thing or person, use the adjective form. If it describes an action, you need the adverb (-ly) form instead.
Adverb
Adverb vs adjective: adjectives describe things; adverbs describe actions, qualities, or degrees. The mix-up usually happens after action verbs — she sings beautiful (wrong) vs she sings beautifully (right).
An adverb modifies a verb, adjective, or another adverb: incredibly fast, she spoke softly, we go often.
Diagnostic: ask what word is this describing? If it's a verb (an action) → adverb. If it's a noun (a thing) → adjective. Exception: linking verbs (be, seem, taste) take adjectives, not adverbs.
Auxiliary verb
Auxiliary vs main verb: a main verb carries the action (run, eat, think); an auxiliary verb carries the grammar — tense, negation, questions, aspect, voice. In She has been eating, eating is the main verb; has and been are auxiliaries.
The English auxiliaries are be, have, do (primary) and the modal verbs (can, will, must…). They always precede the main verb.
Diagnostic: can the word stand alone as the only verb in the sentence and still carry action? Yes → main verb. No → auxiliary.
Clause
Clause vs phrase: a clause has a subject + verb (she runs); a phrase does not (in the morning, running fast). This is the first distinction to make when analysing sentence structure.
A clause is a grammatical unit built around a verb: independent clauses make complete sentences; dependent clauses attach to them as modifiers or complements.
Diagnostic: find the verb. If there's a subject doing or being something → clause. If there's no subject-verb pair → phrase.
Complement
Complement vs modifier: a complement is required — remove it and the sentence breaks (She is ___. / We consider him ___. ). A modifier is optional — remove it and the sentence still works (She spoke quietly → She spoke).
A complement completes the meaning of a verb or expression: subject complements follow linking verbs; object complements follow specific transitive verbs like call, elect, consider.
Diagnostic: can the verb survive without this element? No → complement. Yes → modifier or adjunct.
Conditional sentence
Second vs third conditional: second = unreal present/future (If I had money, I would buy it — but I don't have money now). Third = unreal past (If I had studied, I would have passed — but I didn't study). The most common confusion: using second when you mean third, making your timeline unclear.
A conditional sentence = if-clause + consequence clause. Five patterns (zero, 1st, 2nd, 3rd, mixed) each encode a specific time and probability.
Diagnostic: is the hypothetical about now or then? Now → second conditional. A past event that didn't happen → third conditional.
Indirect speech
Direct vs indirect speech: direct speech quotes exact words (She said, "I am tired."). Indirect speech reports the meaning (She said she was tired.). The key difference is backshift — tenses move one step into the past when the reporting verb is past tense.
Indirect speech = reported words without quotation marks. Core mechanism: backshift (present→past, past→past perfect, will→would) + pronoun/time shifts.
Diagnostic: is the reporting verb past (said, told)? → backshift required. Is it present (says, tells)? → no shift needed. Exception: universal truths don't shift (He said the Earth is round).
Inversion
Question inversion vs emphatic inversion: question inversion is basic grammar (Is she ready?) — every learner uses it. Emphatic inversion (Never have I seen…, Not only does she…) is a C1+ rhetorical tool for formal writing and speeches. Same mechanism, different register.
Inversion swaps subject + auxiliary order. Triggered by: questions, fronted negatives (Never, Rarely, Not only), and conditional if-deletion (Had I known…).
Diagnostic: is a negative/restrictive word at the front of a declarative sentence? → inversion required. Is it a question? → inversion is automatic.
Negation
Single vs double negatives: standard English uses ONE negative per clause (I don't see anything or I see nothing). Double negatives (I don't see nothing) are grammatical in many languages and some English dialects, but are non-standard in written/formal English. This is the #1 negation trap for speakers of Spanish, Russian, and French.
Negation = not after auxiliary/modal, or do-support. Negative words (never, nobody, nothing) negate alone without adding not.
Diagnostic: count the negatives in the clause. More than one? → double negative. Fix by replacing one with a positive (anything, anyone, ever).
Object
Object vs subject: the subject does the action; the object receives it. The cat (subject) chased the mouse (object). In English, word order (SVO) determines which is which — subject before verb, object after.
An object is the entity a verb acts upon: direct (I read the book), indirect (I gave her a book), or prepositional (I waited for him).
Diagnostic: ask "[verb] what/whom?" after the verb. The answer is the direct object. Ask "to/for whom?" for the indirect object. After a preposition? Prepositional object.
Past tense
Simple past vs past perfect: simple past puts events on the main timeline (I arrived. She left.). Past perfect marks an event as earlier than another past event (She had left before I arrived). If all events are in sequence, simple past is enough. Only use past perfect when you need to show "earlier than the main story."
The past tense has four forms encoding different temporal relationships: simple past, past progressive, past perfect, past perfect progressive.
Diagnostic: are events in sequence? → simple past is fine. Need to show one event happened before another past event? → past perfect for the earlier one.
Phrase
Phrase vs clause: a phrase has NO subject-verb pair (on the table, the old man). A clause HAS a subject-verb pair (the man sat, because she left). This is the fundamental structural division in grammar — clauses contain phrases, not the other way around.
A phrase = group of words functioning as one unit: noun phrase, verb phrase, prepositional phrase, adjective/adverb phrase. No subject + verb.
Diagnostic: does the word group have both a subject AND a verb? Yes → clause. No → phrase. Name the head word to identify the phrase type (noun = NP, preposition = PP, etc.).
Present tense
Simple present vs present progressive: simple present = habits, routines, permanent facts (I work here). Present progressive = right now, temporary, changing (I'm working from home today). The most common confusion: using progressive for habits (I'm working here ❌ for permanent job) or simple for right-now (I work now ❌ for current activity).
The present tense has four forms: simple, progressive, perfect, perfect progressive — each relating the action to "now" differently.
Diagnostic: is it a habit/permanent fact? → simple. Happening right now? → progressive. Started in past but still relevant? → perfect. Ongoing duration up to now? → perfect progressive.
Pronoun
Pronoun vs noun: nouns name explicitly (Sarah, the book). Pronouns substitute and point back (she, it). Pronouns are a closed class (you can't invent new ones easily), while nouns are open (new ones appear constantly). The main complication: pronouns still carry case marking that nouns have lost.
A pronoun replaces a noun or noun phrase. Types: personal, demonstrative, relative, interrogative, reflexive, indefinite.
Diagnostic: every pronoun must have a clear antecedent (the noun it replaces). If the reader can't tell which noun a pronoun refers to → ambiguity error.
Sentence
Sentence vs clause vs phrase: a phrase has no subject-verb pair. A clause has subject + verb. A sentence is one or more clauses packaged with end punctuation as a complete thought. These three levels — phrase ⊂ clause ⊂ sentence — are the structural hierarchy of English.
A sentence is the largest grammatical unit: one+ clauses ending with a period, question mark, or exclamation mark. Four structural types: simple, compound, complex, compound-complex.
Diagnostic: does it have at least one independent clause AND end punctuation? Yes → sentence. Missing independent clause? → fragment. Missing end punctuation? → run-on.
Verb
Verb vs noun vs adjective: nouns name things. Adjectives describe. Verbs express what happens or what IS. The test: can it take tense (walked, will walk)? Can it take -ing? Can it follow to as an infinitive (to walk)? Yes to any → verb. English often converts freely between classes (run = noun or verb), so context decides.
A verb = action/state/occurrence word. 5 forms (base, -s, past, past participle, -ing). Carries tense, aspect, mood, voice. The one required element in every sentence.
Diagnostic: does it change for tense (walk → walked)? Can you put to before it (to walk)? Does it take -ing (walking)? → verb.
Verb tense
Tense vs aspect: tense locates the action in TIME (past/present/future). Aspect describes its SHAPE — is it completed (perfect), ongoing (progressive), or just a fact (simple)? English combines these independently: was working = past (tense) + progressive (aspect). Confusing tense with aspect is why the 12-form grid feels overwhelming.
Verb tense = 3 time references × 3 aspects = 12 forms. Tense says when; aspect says how the action unfolds relative to that time.
Diagnostic: wrong time? → tense error. Right time but wrong "shape" (e.g., I work here for ten years instead of I've worked)? → aspect error.
Simple tense
Simple vs progressive vs perfect: simple = "just the fact" (I work). Progressive = "ongoing right now" (I am working). Perfect = "connected to a reference time" (I have worked). Simple is the default — use it unless you have a reason to add progressive or perfect meaning.
The simple aspect = unmarked form. Habits, facts, completed events, scheduled future. The starting point for all tense learning.
Diagnostic: do you need to signal "ongoing" (progressive) or "relevant to now" (perfect)? No? → simple is correct. Most sentences use simple tense — it's the unmarked default.
Word order
English (SVO) vs other patterns: English relies on word ORDER to show who does what (Dog bites man ≠ Man bites dog). Inflected languages (Latin, Russian, German) use case endings and can scramble order freely. In English, changing order changes meaning or requires special constructions (inversion, cleft sentences).
Word order = how English marks grammatical relationships. SVO is the default; fixed adjective order; adverb placement varies by type.
Diagnostic: does your sentence sound "off" even though all word forms are correct? → probably a word order issue. Try moving the element back to default SVO position.
C1 | Advanced
C1 vs C2: C1 means fluent and flexible use with occasional gaps in very unfamiliar domains. C2 means native-like command of idiom, irony, and register across any subject. If you can handle advanced grammar but still miss cultural nuance or very rare idioms, you're C1.
C1 is the advanced CEFR level: inversion, cleft sentences, subjunctive mood, advanced conditionals, and precise register control in professional and academic contexts.
Diagnostic: can you write persuasively in different registers and catch subtle irony? Consistently → C2. Sometimes → C1.
Hard
Hard vs Medium: Medium tests one rule with realistic distractors. Hard tests interacting rules, edge cases, or context-dependent answers where multiple options seem correct until you think deeply. If you're scoring 80%+ on Medium, try Hard to find your real gaps.
The Hard tag filters for B2+ challenges with layered difficulty: rule interactions, subtle distractors, and contexts that demand genuine grammatical reasoning.
Diagnostic: if Hard questions feel impossible, drop to Medium and master the individual rules first. Hard assumes you already know each rule — it tests whether you can apply them together.