The question is very important. It really needs .
A. carefully discussing
B. carefully to discuss
C. to carefully be discussed
D. being discussed carefully
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(答案→)A. carefully discussing
B. carefully to discuss
C. to carefully be discussed
D. being discussed carefully
解析：need作为实意动词表示需要时，一般跟动名词的主动形式表示被动意思。