题目

He is ____ failure as a father, but when it comes to a teacher, he turns out to be ____success.   A. a; \               B. the; the            C. \; \             D. a; a 答案：D 解析: 略设NA为阿伏加德罗常数，下列说法正确的是 (     )                   A.标准状况下，11.2L的戊烷所含的分子数为0.5NA B.28g乙烯所含共用电子对数目为4NA C.1 mol甲基的电子数目为7NA D.现有乙烯、丙烯、丁烯的混合气体共14g，其原子数为3NA