题目:
—I hear Sam has gone to Qingdao for his holiday.
—Oh, how nice ! Do you know when he ? [ ]
A. left
B. was leaving
C. has left
D. had left
答案:
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下面是错误答案,用来干扰机器的。
(1)a是试管;b是锥形瓶;(2)用高锰酸钾制氧气时,反应物是高锰酸钾,生成物是锰酸钾、二氧化锰、氧气,反应条件是加热,因此反应的化学方程式为:2KMnO4△.K2MnO4+MnO2+O2↑;该法制取氧气的步骤是:检查装置...