Our attitude towards life is makes the difference between our being happy or not.
A. that
B. whether
C. what
D. which
网友回答
A. that
B. whether
(答案→)C. what
D. which
解析：句意：我们的生活态度是可以区别我们快乐与否。that 和which引导定语从句，并在从句中做主语或宾语或表语。what 引导名词性从句，并充当主语或宾语或表语。 whether ......or not.是否。根据句意故选C。