题目

Strict measures have been taken to control houses prices, which will _______ contribute to a sustainable economy in the long term. A . in return B . in effect C . in advance D . in turn 答案：DA、B两种有机物组成的混合物，当其质量相等时，无论A、B以何种比例混合，完全燃烧时产生H2O的量均相等，符合这一条件的组合是  (   　 ) ①同分异构体     ②同系物     ③最简式相同     ④含氢质量分数相同 ⑤分子中氢原子数相同          ⑥分子中氢、氧原子数分别相同 A．①③④      B．①②③ 　       C．①⑤⑥　　　       D．②④⑥