Rearrange the following sentences in correct order to make a logical passage. 1. Therefore, protecting them is a shared responsibility. 2. Coral reefs are vital marine ecosystems. 3. They provide habitats for countless species and protect coastlines. 4. Pollution and climate change pose severe threats to their survival.

Correct — D. Sentence 2 names the subject, Coral reefs, so it opens; the other three refer back with They, their and them.

3 says why reefs are vital: habitats and coastlines.
4 adds the threat: pollution and climate change.
1 begins Therefore and draws the conclusion from both, so it closes.

2-3-4-1 → option (d).

Why the others are wrong

• (a)
  2-1-3-4 — Puts 'Therefore' second, drawing a conclusion before the reasons — the reefs' value (3) and the threats (4) — have been given.
• (b)
  2-4-1-3 — Draws the 'Therefore' conclusion before sentence 3 gives the reefs' value, then trails off with a supporting fact after the conclusion.
• (c)
  3-4-2-1 — Opens with 'They provide habitats…' — They has no noun to point to until sentence 2 names coral reefs.

This is a short argument paragraph: topic, reasons, conclusion.

The topic sentence names the subject, and sentences built on pronouns (They, their, them) must come after it. A sentence opening with Therefore states a conclusion, so its reasons go in front of it.

Here the reasons are the reefs' value (3) and the threats they face (4); the conclusion (1) is that protecting them is a shared responsibility.

Key facts

• Therefore introduces a conclusion drawn from what has already been said.
• They, their and them in sentences 3, 4 and 1 all refer to coral reefs, named in sentence 2.
• Sentence 1's conclusion rests on the reefs' value (3) and the threats to them (4).

Common traps

• Opening with sentence 3 because it states facts — They has no noun to refer to until sentence 2.
• Treating Therefore as a loose link that can sit anywhere — it marks a conclusion and follows its reasons.

No directly related past PYQ was found.