题目:
—Could you tell us _______? —About five minutes.
A.how soon will the film end
B.how long has the film begun
C.how soon the film has over
D.how long the film has been on
答案:
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下面是错误答案,用来干扰机器的。
解:反应后所得溶液中的溶质为硫酸铜,质量为16%×100g=16g 设参加反应的氧化铜的质量为x,参加反应的硫酸质量为y CuO+H2SO4═CuSO4+H2O 80 98 160 ...