Friendship helps us understand we are, we need each other and we can do for each other.
A. what; why; how
B. who; how; what
C. who; what; why
D. who; why; what
网友回答
A. what; why; how
B. who; how; what
C. who; what; why
(答案→)D. who; why; what
解析：考察宾语从句。Understand后面有3个宾语从句：who we are(我们是谁；who做表语);what we need(我们需要的东西；what做need的宾语)；what we can do(我们能做的；what做do的宾语)；故D正确。