－I can’t afford ________ a big house now. But I think I can in the future. －I agree with you.

下列各句中，没有语病的一句是

_______ do you write to your parents– Once a month.

The number of foreign students attending Chinese universities _____ rising steadily since 1990

He can’t have finished his homework last night, ______ he?— No. You see, he is busy doing it now. [ ]