这个标志的含义是提醒车辆驾驶人前方是无人看守铁路道口。
参考答案:错
—We'd better hurry; we'll be late.
— __________. Do you really want to listen to the boring lecture?
A.For what?
B.Take it easy.
C.What on?
D.So what?
伤寒病人血培养在病程第三至第四周时阳性率最高。