问题
选择题
. The teacher __________ have thought Johnson was worth it or she wouldn’t have wasted time on him, I suppose.
A．should
B．can
C．would
D．must
答案
D。
“must+have+过去分词”表示对过去情况的肯定推测。句意为：我想，老师一定认为约翰逊是值得教的，要不然她就不会在他身上浪费时间了。