If you don’t know the word, you can in the dictionary.
A. look it after
B. look it up
C. look for it
D. look at it
网友回答
A. look it after
(答案→)B. look it up
C. look for it
D. look at it
解析：B 考查短语。以动词和副词构成的短语，宾语是代词it/ them大牛股时，必须放在而这中间。“查找，查寻”是look up，故选B。