Question

---How often do you visit your grandparents, Tom ?

---______

1. A.
   Half an hour.
2. B.
   Three hours.
3. C.
   Twice.
4. D.
   Hardly ever.

Answer 1

D
how often意思是多久以后，表示频率，常用频率副词来回答，比如often，never，hardly，once a week等。