—I hear a traffic accident happened yesterday. Was it terrible ?        

—Yes. A car _____ and all the people in it were badly hurt. But luckily, none of them was killed.      [ ]

A. fell over

B. fell behind

C. fell off

D. fell down to

相比较ADSL方式，LAN方式用户端不需要“MODEM”终端，且上下行双向速率对称。