-----What about going to the South Lake for a picnic next weekend?--OK. But I am not su

问题补充：

-----What about going to the South Lake for a picnic next weekend?

----OK. But I am not sure it will rain.

A. why

B. where

C. when

D. whether

答案：

A. why

B. where

C. when

(答案→)D. whether

解析：句意：下周末去南湖郊游怎样？好的。但是我不确定是否会下雨。whether为是否。结合句意，故选D