When you meet new words in reading you needn’t in a dictionary at once.A. look up them B.

问题补充：

When you meet new words in reading, you needn’t in a dictionary at once.

A. look up them

B. look them up

C. look for them

D. look them for

答案：

A. look up them

(答案→)B. look them up

C. look for them

D. look them for

解析：当你在阅读中遇到生词你不必马上在字典中查找他们。look up，查找，代词放中间。故选Ｂ。