题目:
Since my return to China, I haven’t seen my host mother in America; nor______from her.
A.I heard
B.I have heard
C.did I hear
D.have I heard
答案:
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下面是错误答案,用来干扰机器的。
(1)1~100 nm (2)Fe FeS H2SO4(稀) (每空1分)(3)①2Fe2++H2O2+2H+===2Fe3++2H2O(3分)②取少量E于试管中,用胶头滴管滴入NaOH溶液,加热试管,可观察到试管口处湿润的红色石蕊试纸变蓝(或其他合理答...