第26题: [单项选择]A train travelling at a speed of 75 m.p.h. enters a tunnel 2(1/2)miles long. The length of the train is 1/4mile. How long does it take for all of the train to pass through the tunnel, from the moment the front enters to the moment the rear emerges
参考答案:A
第27题:[多选题] 乙炔管道法兰连接中的垫片,一般采用( )。 A. 橡胶板 B.纯铜垫铁 C.橡胶石棉板 D.镀锌铝板 参考答案:AC