---The book is borrowed from the library. You your children touch it with their dirty han

问题补充：

---The book is borrowed from the library. You your children touch it with their dirty hands.

---Sorry.

A. should have let

B. needn’t have let

C. mustn’t have let

D. ought not to have let

答案：

A. should have let

B. needn’t have let

C. mustn’t have let

(答案→)D. ought not to have let

解析：考查情态动词。ought not to have done本不应当做某事。句意：——书借自图书馆，你本不应当让孩子用脏手碰它。——对不起。