年通过总质量为25~50Mt,采用轨道结构为()钢轨。
A. 75kg/m
B. 60kg/m
C. 50kg/m
D. 43kg/m
设计标准为百年一遇洪水其意义是每隔100年出现一次。()
A. 正确
B. 错误
Fog is likely to occur when there is little difference between the dew point and the().
A. relative humidity
B. air temperature
C. barometric pressure
D. absolute humidity