问题补充：
We would have to put off the visit to the Water Cube it rain tomorrow.
A. Would
B. Were
C. Should
D. Could
答案：
A. Would
B. Were
(答案→)C. Should
D. Could
解析：考查虚拟语气。此题省略了if， 只能提前would.还原后的句型为 If it should rain tomorrow ,We would have to put off the visit to the Water Cube .在这种对将来的假设条件句中，可用一般过去时、were to do、should do 这三种形式，没有would do 结构。句意：如果明天下雨的话，我们将不得不推迟参观水立方。故C正确。
