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
- Direct: "I am tired." → Indirect: She said she was tired. (present → past)
- Direct: "I will come." → Indirect: He said he would come. (will → would)
- Direct: "I have finished." → Indirect: She said she had finished. (present perfect → past perfect)
- today → that day; here → there; tomorrow → the next day
Indirect speech reports someone's words without quotation marks. The mechanism: backshift tenses one step into the past, shift pronouns, and adjust time/place expressions.
Rule: if the reporting verb is past (said, told, asked), shift the reported tense back one step. If the reporting verb is present (says), no shift needed.
Verb tense
| Simple | Progressive | Perfect | Perfect Progressive | |
|---|---|---|---|---|
| Past | worked | was working | had worked | had been working |
| Present | work(s) | am working | have worked | have been working |
| Future | will work | will be working | will have worked | will have been working |
Verb tense = time (past/present/future) × aspect (simple/progressive/perfect) = 12 forms. Each slot has a specific job — not just "when" but "how the action relates to its time frame."
Key insight: most learners don't need all 12 at once. Simple covers 80% of communication. Add perfect and progressive as needed.
Past tense
- I walked home. — simple past (completed action)
- I was walking when it rained. — past progressive (in progress)
- I had already left when she arrived. — past perfect (earlier past)
- I had been waiting for an hour. — past perfect progressive (duration up to a past point)
Four past tense forms: simple past (done), past progressive (was happening), past perfect (had already happened), past perfect progressive (had been happening). Each encodes different timing relative to other past events.
Pattern: simple past = the story's main timeline. Past progressive = background action. Past perfect = flashback to something even earlier.
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.
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.
B2 | Upper Intermediate
- ✅ If I had studied harder, I would have passed. — third conditional
- ✅ The report is being reviewed by the committee. — passive progressive
- ✅ Having finished the exam, she left. — participle clause
- ✅ He denied having taken the money. — complex verb pattern
These are B2 patterns — the CEFR upper-intermediate level. At B2 you handle mixed conditionals, all passive forms, participle clauses, and can argue a point clearly. This is the level most universities and employers require.
Marker: if you can write a structured essay and debate an abstract topic, you're B2.
Hard
- Had she not intervened, the situation would have escalated. — inverted conditional
- All distractors are grammatically plausible in other contexts
- Multiple rules interact (e.g., tense + aspect + modality)
- Context determines the answer — no single "rule" is enough
Hard marks upper-intermediate to advanced challenges: B2+, interacting rules, edge cases, plausible distractors, and contexts where pattern-matching fails.
Use "Hard" when Easy/Medium feel trivial and you want to test whether you actually understand a rule versus just recognising surface patterns.