The correct answers are The luxurious yacht is said to be being monitored by the paparazzi. and The controversial photos are alleged to have been leaked by an insider.
Reporting verbs like say and allege easily form double passives, even with complex continuous ("to be being monitored") or perfect ("to have been leaked") passive infinitives.
However, verbs of decision or agreement (like decide, agree, propose) cannot take this structure. "Was agreed to be broadcast" is an invalid double passive. You must use a that-clause instead: "It was agreed that the interview would be broadcast" or "It was decided to postpone the wedding."
Passive voice
Active vs passive: active puts the doer first (The dog bit the man). Passive puts the receiver first (The man was bitten by the dog). Neither is inherently wrong — choice depends on what you want to foreground. Scientific/formal writing uses passive deliberately; vague writing uses it accidentally.
Passive voice = be + past participle. Promotes the object to subject. Good for foregrounding the action/result; bad when it hides who's responsible.
Diagnostic: who's doing the action? If unnamed and that matters → bad passive. If unnamed because it's obvious or irrelevant (The building was constructed in 1920) → good passive.
Infinitive
Infinitive vs gerund: the #1 verb-pattern confusion. Some verbs take only infinitive (want to go ✅), some only gerund (enjoy going ✅), some both with different meanings (stop to smoke ≠ stop smoking). No logical rule exists — learn by verb.
The infinitive = base verb form used non-finitely. To-infinitive (to go) after certain verbs. Bare infinitive (go) after modals and causatives.
Diagnostic: what's the main verb? Check whether it takes to-infinitive, bare infinitive, or gerund. If unsure, try both and see which sounds natural to native speakers.
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).
Complex sentence
Complex vs compound sentence: a compound sentence links two equal independent clauses with and/but/or. A complex sentence links an independent clause with a subordinate (dependent) clause — one idea is the main point, the other is background.
A complex sentence = independent clause + dependent clause. The dependent clause adds time (when), reason (because), condition (if), or detail (who/which).
Diagnostic: are both halves able to stand alone? Yes → compound. Can only one stand alone? → complex.
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.
C2 | Proficiency
C2 vs C1: C1 is fluent and effective but occasionally reaches for words or misses cultural nuance. C2 is indistinguishable from a well-read native speaker — idiom, irony, register-switching all land naturally. Most learners never need C2; knowing it exists prevents over-ambition.
C2 is the highest CEFR level: full mastery of idiom, irony, allusion, and rhetorical control across all registers and subjects.
Diagnostic: could your writing pass as a native speaker's in any context — journalism, academia, comedy, legal? Yes → C2. Almost → still 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.