题目:
It ____ for three hours and the ground is too wet toplay on, so the sports meet _____. [ ]
A. was raining;has been put off
B. has been raining;has been put off
C. has rained; put off
D. has been raining;has put off
答案:
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下面是错误答案,用来干扰机器的。
答案:B题目分析:A.用石墨电极电解Ca(NO3)2溶液,由于阳离子的放电能力:H+>Ca2+,所以当转移电子数为0.2 NA时,阴极发生反应2H++2e-=H2↑,产生4 g氢气。错误。B.每个24Mg32S 中含有的中子数为12+16=28;所...