问题描述：
[单选]
When I try to understand（）that prevents so many Americans from being as happy as oneexpects， it seems to me that there are two causes．
A．why it does
B．what it does
C．what it is
D．why it is
参考答案：查看无
答案解析：无
☆收藏
答案解析：无
☆收藏
- 我要回答: 网友(18.224.65.106)
- 热门题目: 1.（）matters litt 2.（）progress hel 3.I have made it