Having mastered the technology of manned spacecraft, China became the third country in the

world ______ manned spaceflight independently.[      ]

A. to develop    

B. developing    

C. developed    

D. develop

视频采集卡的基本功能是将模拟视频信号经过取样、量化以后转换为数字图像并输入到计算机主机中。视频采集的模拟视频信号可以来自( )。

A．DVD播放器

B．有线电视

C．影碟机(L

D．以上设备均可