击球的用力方向：来球比网底时，在向前用力时还要附加向（）的力，使球不致于落网。
参考答案：上
The world is changing rapidly and sometimes we find it almost impossible to ________ the advances in science and technology.
A．keep up with
B．come up with
C．put up with
D．stay in touch with
神圣罗马帝国
