— does Earth Day come every year? —It comes on April 22.A. WhatB. WhyC. WhenD. Where

问题补充：

— does Earth Day come every year?

—It comes on April 22.

A. What

B. Why

C. When

D. Where

答案：

A. What

B. Why

(答案→)C. When

D. Where

解析：C 根据答语“地球日是4月22日”知，问的是“地球日”是每年的哪一天。故选C。