超车时要重点把握超越前方车辆后驶入原车道的时机，防止返回原车道时发生碰撞。
参考答案：对
We live day by day, but in the great things, the time of days and weeks ____ so small that a day is unimportant.
A．is
B．are
C．has been
D．have been
内源性凝血系统最常用的筛检试验是（）
A.APTT
B.复钙时间
C.CT
D.ACT
E.BT
