问题补充：
--We don’t think we’ll be able to go mountain-climbing tomorrow.
-- the weather turns out fine?
A. How come
B. What if
C. How about
D. Why not
答案：
A. How come
(答案→)B. What if
C. How about
D. Why not
解析：考察交际用语。A怎么会？B要是…又如何？C…怎么样？D为什么不…?结合句意可知B正确。句意：—我们不认为明天我们能够去登山？—要是天气变好了怎么办？
