complete the questions. Write What's or What are............. their phone number?
Answer (1)
To complete the question, the correct form would depend on whether you are referring to a singular or plural subject. If you are asking about one person's phone number, you would say, "What's their phone number?" If you are asking about multiple people, you would say, "What are their phone numbers?"Since the question does not specify the number of people, the most appropriate completion is "What's their phone number?"
