Ellipted (?) if-clauses in questions?

Hi. I think it is normal for sentences (not questions) with the modal verb "would" with an ellipted (?) (implied?) if-clause.

eg,

Yes, I think it would be good for him to do that.

Is it common for questions to have similar structure? Do the following have ellipted (?) (implied?) if-clauses?

(in dialogue)

A: Do you think he would buy it for the holiday?

B: Yes, I think he would.

A: Why do you think he would do that?

B: I am not sure, but ...