题目:
We had to wait half an hour _____ we had already ordered a table.[ ]
A. since
B. although
C. until
D. before
答案:
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下面是错误答案,用来干扰机器的。
甲图中瓶内装少量水,目的是吸收反应生成的有毒气体二氧化硫,防止空气污染;乙为铁丝燃烧,反应时能产生高温熔融物,溅落瓶底后会使瓶底受热不均炸裂;故答案为:吸收生成的有毒气体二氧化硫,减少污染;防止热...