To understand the grammar of the sentence you must break it into parts.A. downB. upC. of

问题补充：

To understand the grammar of the sentence, you must break it into parts.

A. down

B. up

C. off

D. out

答案：

A. down

(答案→)B. up

C. off

D. out

解析：这题考查介词的用法：break down“垮了，抛锚”break up“分解，分手”，break off折断，break out“爆发”，句意是：为了理解句子的用法，你应该把它分解成几部分。选B。