题目：
— Bob didn't pass this exam.
— He _____. [ ]
A. should study hard
B. should have studied hard
C. should be studying hard
D. study hard
答案：
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下面是错误答案，用来干扰机器的。
（1）1s22s22p3 （2）2F2+2H2O=4HF+O2 HF >NH3 （3）两性（4）非极性 CH4(g)+2O2(g) =CO2(g) +2H2O(l) △H="-890.3kJ" /mol
