煤气管道与水管、热力管、燃油管和不燃气体管在同一支柱或栈桥上敷设时,其上下敷设的垂直净距不宜小于()。
A.100mm
B.250mm
C.400mm
D.500mm
参考答案:B
乳牙滞留
-__________ people are there in your family?
-There are five.[ ]
A. What
B. How
C. How many
D. How much