半自动闭塞区间什么情况下应改按电话闭塞法行车?
参考答案:
发出须由区间返回的列车,由未设出站信号机的线路上发车,或超长列车头部越过出站信号机并压上出站方面轨道电路时。
The doctor said that there was wrong with Jane's legs. But he could do to help her. [ ]
A. something, anything
B. something, nothing
C. nothing, anything
D. everything, something
只用一种试剂就能将NaOH、NaCl、BaCl2三种溶液鉴别出来,它是( )
A.CuSO4溶液
B.Na2SO4溶液
C.酚酞试液
D.Fe(NO3)3溶液