一个绕地球做匀速圆周运动的人造地球卫星，它的轨道半径增加到原来的2倍后，仍做匀速圆周运动，则[ ]

A. 根据公式F＝G可知地球提供的向心力将减小到原来的1/4

B. 根据公式a＝可知卫星运行的向心加速度减小到原来的1/2

C. 根据公式v＝ωr可知卫星运动的线速度将增大到原来的2倍

D. 根据公式F＝可知卫星所需的向心力将减小到原来的1/2

An Intranet is (66) the application of Internet technology within an internal or closed user group. Intranets are company (67) and do not have a (68) connection to the Internet. Used properly an Intranet is highly effective corporate tool, capable of regularly (69) information to empower the workforce with the information needed to perform their roles. Used in this way, an Intranet represents a step towards the (70) office.

A．update

B．updated

C．updates

D．updating