These are the words you must attach great importance when you write the essay.
A. in which
B. to which
C. which
D. that
网友回答
A. in which
(答案→)B. to which
C. which
D. that
解析：句意：当你写作文的时候，这些是你必须重视的词汇。这里是定语从句，先行词是words，attach… to把……附加于；which在这里做介词to的宾语，判断用哪个介词可以根据先行词或在定语从句中的谓语动词连用的介词，故选B.