题目

分子与原子的主要区别是A．分子的体积比原子大。B．分子的质量比原子的质量大C．分子可直接构成物质，原子则要先构成分子后再构成物质D．在化学反应中分子可分，原子不可分 答案：D解析:略Not once ________ to Michael that he could one day become a top student in his class.A．occurred itB．it did occurC．it occurredD．did it occur