It’s difficult to these old books for some of them none of the classification.A. look fo

问题补充：

It’s difficult to these old books for some of them none of the classification.

A. look for; are belonging to

B. put up; belong

C. sort out; belong to

D. pick up; are belonged to

答案：

A. look for; are belonging to

B. put up; belong

(答案→)C. sort out; belong to

D. pick up; are belonged to

解析：动词短语用法辨析。Look for 寻找；put up张贴，留宿；sort out分类；pick up捡起；用车接；无意中学会；接受信号；康复。恢复；染上…；belong to属于（没有被动语态，没有进行时）；句意：把这些旧书分类很困难，因为他们不属于任何一种类别。故C正确。