104型制动机发生紧急制动后,需经过()秒才能对列车管进行充气,这样可防止列车发生剧烈纵向冲动,甚至造成断钩事故。
参考答案:15
By the end of last year,another new theme park completed in that area. [ ]
A. was being
B. would be
C. has been
D. had been
如图所示,表示晶体物质凝固过程的图像是[ ]
A.
B.
C.
D.