The correct answers are I am studying at the library today., The science books are on the third floor., and It is very quiet in the library this morning.
Use at or in for the building itself (at the library for the general location, in the library for being inside).
However, when talking about the levels or floors of a building, always use on (e.g., on the second floor, on the third floor).
Preposition
- ✅ interested in — ❌ interested on
- ✅ good at football — ❌ good in football
- ✅ depend on — ❌ depend of
- ✅ arrive at the station — ❌ arrive to the station
Prepositions link nouns to the rest of the sentence: time (at 5pm), place (in London), manner (with care), abstract (afraid of). Most are idiomatic — the "correct" preposition must be memorised with each verb/adjective combination.
Rule: there is no universal rule. English prepositions are learned by combination: interested IN, good AT, depend ON, afraid OF. Your native language's equivalent will often mislead.
Phrase
- the red car — noun phrase (functions as one noun unit)
- on the table — prepositional phrase
- has been running — verb phrase
- very quickly — adverb phrase
A phrase is a group of words that functions as a single unit WITHOUT a subject + verb pair. Types: noun phrase, verb phrase, prepositional phrase, adjective phrase, adverb phrase.
Key distinction: a phrase lacks a subject-verb pair. If it has subject + verb → it's a clause, not a phrase. Phrases are the building blocks clauses are made of.
Sentence
- She left. — simple (one independent clause)
- She left, and he stayed. — compound (two independents)
- She left because she was tired. — complex (independent + dependent)
- She left because she was tired, and he stayed. — compound-complex
A sentence = one or more clauses forming a complete thought, ending with terminal punctuation. Four types based on clause structure: simple, compound, complex, compound-complex.
Minimum requirement: at least one independent clause with a subject + finite verb. Without that → fragment.
Present tense
- I work here. — simple present (habit/permanent)
- I am working now. — present progressive (happening right now)
- I have lived here for 10 years. — present perfect (started past, still true)
- I have been waiting for an hour. — present perfect progressive (duration up to now)
Four present tense forms: simple (habits/facts), progressive (now/temporary), perfect (past → present relevance), perfect progressive (ongoing duration). Each encodes a different relationship between the action and the present moment.
Trap: "I am living here for 10 years" ❌ — started in the past + still true = present PERFECT (have lived/have been living), not progressive.
A1 | Elementary | Beginners
- ✅ My name is Anna. — present simple of be
- ✅ Where is the station? — basic *wh-*question
- ✅ I have two brothers. — possession with have
- ✅ She likes coffee. — third-person -s
These are A1 sentences — the starting level of the CEFR framework. At A1 you can introduce yourself, ask and answer simple personal questions, and handle basic everyday transactions using present tense, be/have/do, and core vocabulary.
If you can say these but freeze at normal speaking speed, you're solidly A1 — and that's exactly where to start.
Medium
- If I were you, I would apologise. — one rule (second conditional), but distractors like was tempt you
- Answers require active thought, not instant pattern recognition
- Vocabulary and context are realistic, not artificially simplified
- Usually tests one rule, but the wrong answers are plausible
Medium marks middle-difficulty challenges: A2–B1, one rule tested, but with realistic distractors that require genuine understanding.
Use "Medium" when Easy feels too obvious but Hard feels overwhelming. This is where most productive learning happens — the sweet spot of difficulty.