近年来数据通信中采用较多的差错控制方式为（）。
A.前向纠错
B.检错重发
C.回程校验
D.混合纠错检错
参考答案：B
He to go to Beijing today, but he postponed the trip when he heard that there would be a downpour at noon.
A．was intending
B．would intend
C．had intended
D．intended
风湿性心脏病二尖瓣狭窄时心脏呈（）
A.靴形心
B.主动脉型心
C.梨形心
D.横位心
E.滴状心
