取心钻进过程包括形成岩心、保护岩心和取出岩心等（）主要环节。
A.两个
B.四个
C.五个
D.三个
参考答案：D
数据库管理系统(DBMS)管理并且控制对 【13】 资源的使用。
You can't help wondering how much he has changed. He is not what he _____. [ ]
A. would be
B. used to be
C. was used to be
D. was used to being
