问题
选择题
— Lily is a happy girl, but today she seems in a bad mood.
— Something ________ to her.
A．must happen
B．should have happened
C．could have happened
D．must have happened
答案
答案：D
根据句意应该是Lily过去肯定发生了一些事，should have happened过去本应该做某事 could have happened过去可能做了某事，must have happened过去肯定做了某事，所以答案D。