套餐签约以后，（）取消吗？
A.不可以
B.可以
C.以生效后的可以
D.未生效的可以
参考答案：D
— I'm going to San Francisco for a couple of days.
— ____ . I wish I could get away for a while. [ ]
A. It doesn't matter
B. Forget it
C. I really envy you
D. I can't agree more
滑动摩擦力的大小与两个物体 ______以及 ______的大小有关．接触面越 ______，摩擦力越大；压力越 ______，摩擦力越 ______．
