There is much truth in the idea _ kindness is usually served by frankness.
A. why
B. which
C. that
D. whether
网友回答
A. why
B. which
(答案→)C. that
D. whether
解析：本题考查同位语从句，前面有一个名词作为先行词Idea,后面句子成分完整，所以不可能为定语从句，又因为从句的内容就是先行词 idea，所以判断该句为同位语从句，句意：这是很有道理的想法,仁慈通常装的坦率。选择C。