题目

15. The country life he was used to _____ greatly since the opening policy. A. change              B. has changed C. changing            D. having changed 答案：B 解析: 选B。The country life 是定语从句的先行词，同时也是句子的主语。而he was used to是定语从句，省略了关系代词that/which。一个角的余角和补角也互为补角，这个角是（ ）度.  A．90°B．75°C．45°D．15°