Complete the museum guide's fascinating tale about a historical feline.
Sir Paws-a-Lot, an 18th-century aristocat, is widely believed _____ the concept of the 3 PM afternoon nap.
The correct answer is to have invented.
When we use a passive reporting verb (like is believed, is said, is known) followed by an action that happened before the time of reporting, we use the perfect infinitive (to have + past participle).
"To invent" would incorrectly suggest he is inventing it now or in the future, while "that he invented" requires the impersonal structure: "It is widely believed that he invented..."
Passive voice
If your writing has been called "weak" or "evasive" — Mistakes were made, It was decided that... — you've hit the passive voice's main pitfall. Used deliberately, the passive is precise and useful: it foregrounds the action when the doer doesn't matter. Used by default, it makes prose feel like nobody's responsible for anything.
The passive voice is formed with be + past participle and turns the object into the subject: The chef cooked the meal → The meal was cooked (by the chef). Useful when the action matters more than the doer; overused, it makes writing feel evasive.
Infinitive
If you've ever written I enjoy to swim or He let me to go and only later learned why both are wrong — you've hit the infinitive's main puzzle. English is fussy: some verbs demand the to-infinitive, some demand the bare infinitive, some demand the gerund, and a few accept multiple options with different meanings (remember to lock vs remember locking).
The infinitive is the basic form of a verb, used non-finitely. The to-infinitive (to go) follows verbs like want, decide, plan; the bare infinitive (go) follows modal verbs (can, will) and causatives (Let him go).
Indirect speech
If you've ever tried to retell what someone said and ended up with a verb-tense mess (She said she will come — wait, would come?), you've hit indirect speech. The rules look intricate but reduce to one move: when the reporting verb is past, shift everything in the reported clause one step into the past. Master that and reporting other people's words stops being a guessing game.
Indirect speech reports what someone said without quoting them: "I like apples" → He said that he liked apples. The core mechanism is backshift — tenses retreat one step into the past — plus pronoun and time-expression shifts.
B2 | Upper Intermediate
If a university admissions team or visa office has ever asked you for an English test score, B2 is probably the level they had in mind. It's the threshold where your English stops being a constraint and starts being a tool — and the line between B1 and B2 is often the line between "stuck in beginner classes" and "ready to study or work in English."
B2 is the upper-intermediate level in the CEFR framework, demanding flexible control of mixed conditionals, passive voice across tenses, reported speech with backshifting, and participle clauses.
Difficulty: Hard
If easy and medium questions are clicking but you still feel exposed in real conversation or formal writing, you've outgrown the basics. Hard material is where the gaps you didn't know you had show up: the distractor that "sounds right", the rule that interacts with another rule, the case where context changes the answer. It's where genuine fluency is built.
The Hard difficulty tag marks upper-intermediate to advanced challenges — typically B2 and above. Interacting rules, edge cases, plausible distractors, and contexts that require genuine understanding rather than surface pattern-matching.