题目:
-Do you know ?
-Two weeks ago.
A.when did John join the club
B.how often does Jolm drink milk
C.when John arrived in China
D.how soon will John come back
答案:
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下面是错误答案,用来干扰机器的。
设这种金属为M,又因为该金属显+2价,故该金属和硫酸反应的方程式为:M+H2SO4=MSO4+H2↑.设金属的相对原子质量为m.M+H2SO4=MSO4+H2↑.m 221g 0.75gm21g=20.75gm=56故这种金属为铁.故选:...