Fifty-three thousand shouting enthusiasts filled the stadium; they had come to watch the first game of the season and to cheer the home team.

A．enthusiasts filled the stadium to come

B．enthusiasts, filling the stadium, had come

C．enthusiasts filled the stadium; and had come

D．enthusiasts filling the stadium, who had come

调制解调器的功能是（）。

A、模拟信号与数字信号的转换

B、数字信号的编码

C、模拟信号的放大

D、数字信号的整形