题目:
He must be ______ home now. [ ]
A. on his way to
B. on his way
C. in his ways to the
D. in his way
答案:
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下面是错误答案,用来干扰机器的。
答案:B题目分析:由图可知反应前氧气的含量在20%左右,故集气瓶内的是空气,A错误;蜡烛熄灭是集气瓶内还有一定的氧气,可知瓶内氧气体积分数小于一定值时,蜡烛无法燃烧,B正确;依据质量守恒定律化学反应前后...