Step 1: Understand the question tag.
In question tags, the auxiliary verb must match the verb used in the main clause. Since the main clause uses "can," the question tag should also use "can." Additionally, as the subject is plural ("they"), the correct form is "can’t they."
Step 2: Analyze each option.
- (A) can’t they: Correct. This is the correct question tag for a statement using "can" in the affirmative form.
- (B) mustn’t they: Incorrect. "Must" is not used in the main clause, so "mustn't" is not appropriate.
- (C) won’t they: Incorrect. "Won’t" is used with "will," but the main verb here is "can."
- (D) aren’t they: Incorrect. "Aren’t" is used with "be" in the verb, but the verb here is "can."
Step 3: Conclusion.
The correct question tag is "can’t they."