下列受压元件维修中，（）属于重大维修。
A.更换
B.矫形
C.改变用途
D.挖补
E.改变运行参数
F.改变介质
参考答案：A, B, D
They said that not all trainees would be suitable for the jobs _____ they were being trained.
A．in which
B．for which
C．in that
D．for that
（）是一个处处与重力方向垂直的连续曲面。
A.海平面
B.水平面
C.水准面
D.竖直面
