深孔滚压头从工件孔中退出时，受到（）的轴向力，滚柱向左移动，外径减小，不会碰伤已滚过的表面。
A.向上
B.向下
C.向右
D.向左
参考答案：D
As a child, Johnson would sit on the steps alone, _______ the sun ______ down.
A．watched; going
B．watching; went
C．watching; go
D．watched; went
请举出几种常用的等渗溶液和高渗溶液？
