The police are looking for a missing boy who is believed a white pullover and a blue jea

问题补充：

The police are looking for a missing boy, who is believed a white pullover and a blue jeans.

A. wearing

B. to be wearing

C. to wear

D. having worn

答案：

A. wearing

(答案→)B. to be wearing

C. to wear

D. having worn

解析：考查非谓语动词作宾语补足语用法。根据第一句警察正在寻找一个失踪的男孩，说明谈论的是正在进行的事情，故使用进行式，排除CD。Believe sb to be认为某人…；故后面使用不定式的进行式。B正确。