it rain tomorrow, we would have to put off the visit to the Yangpu Bridge.
A. Were
B. Should
C. Would
D. Will
网友回答
A. Were
(答案→)B. Should
C. Would
D. Will
解析：句意：如果明天下雨，我们将不得不取消参观杨浦大桥。前半句是对将来情况的虚拟，正常语序是If it should rain tomorrow。省略 if 后，要将 should提到主语之前，引起倒装。所以选B。