高柱信号机距离正线及通行超限列车的线路中心线最小距离为()mm。
A.1850
B.2440
C.1750
D.1900
参考答案:B
硫酸的摩尔质量是
A.98
B.98g
C.98mol
D.98g/mol
The old man has two sons, __________ lives with him, so he has always felt lonely since his wife’s death.
A.both of them
B.both of whom
C.neither of them
D.neither of whom