在IEC60870-5-102中，控制站未收到响应报文，重发原报文，最大重发次数为（）。
A.1次；
B.2次；
C.3次；
D.4次。
参考答案：C
Since he started high school, he’s come to school by bike_____. [ ]
A. on his own
B. by his own
C. in his own
D. with his own
图示为汽车转向二自由度模型，描述其运动的微分方程为
