The topic, we devoted a heated discussion last night, is a hot issue at present.
A. which
B. where
C. to which
D. for which
网友回答
A. which
B. where
(答案→)C. to which
D. for which
解析：考查非限制性定语从句。句意：昨晚，我们热烈讨论的那个话题，现在是一个热门问题。根据逗号可知，是非限制性定语从句，devote...to sth把......投入到......。句中的devoted缺少介词to，故选C。