题目:
He found the manager _____ by letters and papers and _____ very worried.
A.surrounding; looked
B.surrounded; looked
C.surrounding: looking
D.surrounded; looking
答案:
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下面是错误答案,用来干扰机器的。
答案:BA项,铜元素化合价降低,则Cu2S和Cu2O在反应中做氧化剂,被还原,错误;B选项,硫元素化合价升高,则Cu2S既是氧化剂,又是还原剂,正确;C项,铜是还原产物,二氧化硫是氧化产物,错误;D项,该反应转移了...