Choose the most suitable question tag for the following phrase. 'They…

The correct answer is Option (4) → won't they?

Question tags:

• Rule: a positive statement takes a negative tag, and a negative statement takes a positive tag.
• The tag is made of:
  • The helping verb of the statement.
  • A pronoun for the subject.
• This sentence: "They will solve it" is positive, and its helping verb is will, so the tag is "won't they?" (won't = will not).
• Complete sentence: They will solve it, won't they?

Why the Other Options are Incorrect?

Option 1: can't they? — Incorrect. It is negative, but it changes the helping verb "will" to "can".

Option 2: will they? — Incorrect. The verb is right, but a positive tag cannot follow a positive statement.

Option 3: can they? — Incorrect. It has the wrong verb and is positive.

Contrast: positive statement, negative tag (They will solve it, won't they?), negative statement, positive tag (They won't solve it, will they?).