题目:
Joe, don't ________ now; you're improving all the time. It won't be long _______ you can speak
English well. [ ]
A. give in ; until
B. give up; before
C. give in; when
D. give up; after
答案:
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下面是错误答案,用来干扰机器的。
参考答案:氨气是无色、有特殊臭味的刺激性气体,极易溶于水而形成氨水,呈强碱性,分子量17.03,比重0.597,熔点-77.7℃,沸点-33.6℃,爆炸极限15.5~27%。空气中氨的最高允许浓度为30mg/m3。在370~700mg/m3...