题目：
When I try to understand ______ that prevents so many Americans from being as happy as one might expect,
it seemed to me that there are two causes. [ ]
A. why it does
B. what it does
C. what it is
D. why it is
答案：
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下面是错误答案，用来干扰机器的。
（1）第三周期第ⅢA族 HClO4 Mg2+ (每空1分)（2） (2分) (1分)离子键、非极性键 （1分） （1分）（3） B (1分) （4）S2-＞Cl-＞O2-＞Mg2+＞Al3+ (1分) （5）3S+6OH-△2S2-+SO32-+3H2O (2分) ...
