题目

Mr. Smith owns _____ collection of coins than anyone else I have ever met.    A. larger     B. a larger     C. the largest     D. a large 答案：BNA代表阿伏加德罗常数。已知C2H4和C3H6的混合物的质量为a g，则该混合物( )A.所含共用电子对数目为(a/7+1) NAB.所含原子总数为aNA/14C.燃烧时消耗的O2一定是33.6 a/14LD.所含碳氢键数目为aNA/7