离地面高度等于地球半径的高处，重力加速度的大小是地球表面处的[ ]
A．2倍
B．4倍
C．
D．
答案：D
I have reached a point in my life ______ I am supposed to make decisions of my own. [ ]
A. which
B. where
C. how
D. why
英译汉：“roll test；stacking test；vibration test”，正确的翻译为( )。
A．滚动试验；堆码试验；振动试验 B．堆码试验；滚动试验；振动试验C．振动试验；堆码试验；滚动试验 D．滚动试验；振动试验；堆码试验
