Oracle数据库中重建controlfile文件只能在（）阶段进行。
A.nomount
B.mount
C.open
D.close
参考答案：A
_______ surprised me most was that she had become a famous singer.
A．That
B．It
C．What
D．This
己烷精馏塔使用的塔板是（）。
A.筛板
B.泡罩塔板
C.浮阀塔板
D.喷射型塔板
