Question

---How often are the Olympic Games held?

---________ four years．

1. A.
   Every
2. B.
   Each
3. C.
   In
4. D.
   For

Answer 1

A
how often意为“多久一次”，问的是频率．四个选项中只有Every four years表示“频率”，意为“每隔四年一次”．