纵向车间安全距离，是指在前车因突然情况紧急制动时，后车能在两车间把车安全停住的距离。
参考答案：对
From a _____ look in his eyes, I bet he didn't get the hang of the meaning of the poem.
A．frightened
B．satisfied
C．puzzled
D．excited
阀门拆下来而又不能同时按上阀门或连接管道的情况下，可以不加堵盲板，允许长期敞口。（）
