Whose is this doll? a) It's Marina. b) It's Marina's.

The correct answer is b) It's Marina's. Explanation: The question 'Whose is this doll?' asks about possession. Option b) uses the possessive form 'Marina's', indicating that the doll belongs to Marina, making it grammatically and contextually correct. Option a) simply states 'It's Marina' which does not show that she owns the doll