life exists on any other planet in the solar system still remains a question. A. WhyB. Wh

问题补充：

life exists on any other planet in the solar system still remains a question.

A. Why

B. Whether

C. How

D. Where

答案：

A. Why

(答案→)B. Whether

C. How

D. Where

解析：考查主语从句：句意：是否在太阳系的其他星球上有生命的存在还是个问题。通过句意判断应该是whether连接主语从句，选B。