随车机械师原则上每2小时须巡视检查1次，单程运行不足2小时则巡视检查1次。
参考答案：对
一列士兵队伍正以某一速度v1做匀速直线运动，一通信员以不变的速率跑步从队伍尾部赶到排头，又从排头回到队尾，在此过程中通信员的平均速度为v2，则（ ）
A．v1＞v2
B．v1=v2
C．v1＜v2
D．没有给出具体的数据，无法判断
—What a careful boy you are!
—Thank you. In fact, Tom does everything ___ than me.
A. more carefully B. more careful C. much careful
