问题补充：
This cake is very sweet. Youa lot of sugar in it.
A. should put
B. could have put
C. might put
D. must have put
答案：
A. should put
B. could have put
C. might put
(答案→)D. must have put
解析：考查情态动词。must have done 肯定做了某事，表示对过去的肯定推测。句意：蛋糕非常甜，你肯定在里面放了很多糖。所以选D。could have done 本可以做而没做
