题目

已知一组有机物的分子式通式，按某种规律排列成下表，各项物质均存在数量不等的同分异构体。其中第12项的异构体中，属于酯类的有 ( 不考虑立体异构 ) （ ） 项序1234567… … 通式… … A . 8种 B . 9种 C . 多于9种 D . 7种 答案：B---What’s wrong with you, Mr. Keller?    --- I’ve had a very bad headache for two days. At first, I ______ I caught a cold, but the medicine ______.    A. thought, hasn’t worked                   B. had thought, didn’t work  C. thought, hadn’t worked                  D. have thought, hasn’t worked