The correct answers are Professor Higgins said that octopuses have three hearts and Professor Higgins said that octopuses had three hearts.
When reporting a general truth or a scientific fact, "backshifting" (changing the present tense to the past tense) is optional.
You can keep the present tense ("have") because the fact is still true today. However, standard sequence-of-tenses rules also allow you to backshift to the past tense ("had") to match the past reporting verb ("said").
"Had had" is incorrect because past perfect implies they no longer have three hearts. "Says... had" is incorrect because a present-tense reporting verb ("says") cannot be followed by a backshifted past tense if the original statement was in the present.
Indirect speech
Indirect speech (also called reported speech) is how you tell someone what another person said without quoting their exact words. "I like apples" → He said that he liked apples. The signature move is backshift: tenses move one step into the past when the reporting verb (said, told, thought) is itself in the past — present becomes past, past becomes past perfect, will becomes would, can becomes could.
Pronouns and time expressions also shift to fit the new perspective: "I'll see you tomorrow" → She said she'd see me the next day. Mastering this is essential for B1+ communication, especially in writing.
Verb tense
Verb tense is the verb form that signals when the action happens. English has three time references — past, present, and future — combined with three aspects (simple, progressive, perfect, plus perfect progressive) to give twelve standard tense forms in total.
Each tense form carries specific meaning beyond just "when". I worked (simple past) and I have worked (present perfect) both refer to past action, but only the second connects that action to the present. Picking the right tense is what makes English narratives clear; the wrong one makes meaning subtly drift.
Past tense
The past tense is how English talks about events finished before now. It comes in four flavours: simple past (I walked) for completed events, past progressive (I was walking) for actions ongoing at a past time, past perfect (I had walked) for events before another past event, and past perfect progressive (I had been walking) for ongoing events leading up to a past point.
Choosing the right one is what makes past narratives clear instead of murky. When I arrived, she ate dinner is technically grammatical but means something different than had eaten (already done) or was eating (in progress when you arrived).
Present tense
The present tense in English has four forms: simple present (I work) for habits, general truths, and stative descriptions; present progressive (I am working) for actions happening right now or temporary situations; present perfect (I have worked) for past actions with present relevance; and present perfect progressive (I have been working) for ongoing actions continuing into the present.
The simple/progressive distinction is one of the trickiest jumps for learners — I work in Paris (habitual) and I'm working in Paris (temporary, right now) feel almost identical but signal different things. Pick wrong and your meaning subtly shifts.
Sentence
A sentence is the largest grammatical unit in writing — one or more clauses expressing a complete thought, ending with a period, question mark, or exclamation mark. English sentences come in four structural types: simple (one independent clause), compound (two or more independent clauses joined), complex (independent + dependent clause), and compound-complex (multiple independent + dependent clauses).
Mastering sentence types is what lets you vary rhythm in writing. All-simple sentences read as choppy; all-complex sentences read as dense. Mixing them is what makes prose breathe.
B2 | Upper Intermediate
B2 is the upper-intermediate level in the CEFR framework, sitting between B1 and C1. At B2 you can read editorials, follow most TED talks without subtitles, and hold extended conversations on abstract topics — including topics outside your everyday life.
Grammatically, B2 means flexible control of mixed conditionals, passive voice across tenses, reported speech with proper backshifting, and participle clauses. B2 is the standard target for university entrance exams (IELTS 5.5–6.5, TOEFL 87–109) and most skilled-migration thresholds — knowing whether you're there shapes your study plan.
Difficulty: Hard
The Hard difficulty tag marks questions and challenges aimed at upper-intermediate to advanced learners — typically B2 and above. Expect interacting rules, edge cases, distractors that look right at first glance, and contexts where the surface meaning and the grammatical answer don't match.
Filter by Hard when you're past the basics and want material that genuinely tests your understanding. These questions catch the gaps your textbook didn't — register-sensitive choices, exception cases, mixed conditionals, the difference between would have been and had been.