发生石油液化气中毒事故后，必须立即将中毒者移至空气新鲜处，安置其休息并注意保暖。
参考答案：对
牛具有哪些生物学习性？
It ___ to be raining when we went to see him off at a railway station.
A．happened
B．had happened
C．took place
D．took
