It is in Steven Spielberg' s first film, Jaws, ____ a big white shark attacks swimmers ____ are spending their holidays in a small village by the sea.

A．where; who

B．which; that

C．that; that

D．where; that

凸轮机构广泛用于自动化机械中，凸轮机构中主要以凸轮为主动件，从动件的运动规律是由（）决定的。

A.凸轮的转数

B.凸轮轮廓曲线

C.凸轮机构的连接

D.凸轮的基园和压力角