— Why does the boy keep crying?— It is he has lost his favorite car model.A. since B. so

问题补充：

— Why does the boy keep crying?

— It is he has lost his favorite car model.

A. since

B. so

C. when

D. because

答案：

A. since

B. so

C. when

(答案→)D. because

解析：考查连词：A. since自从，B. so所以，C. when当,…时候，D. because因为，句意：为什么这些男孩一直在哭？--是因为他失去了最喜欢的汽车模型。Because引导表语从句，回答why的问题。选D。