Which statement is TRUE concerning protect
题型：单项选择题
问题：
Which statement is TRUE concerning protection of double bottom tanks against excessive pressure? （）
A.Each vent for the tank must be equal to the area of the tank filling line
B.The tanks must be protected by overflows
C.The total area of the vents or the overflow shall be at least equal to the area of the fill line
D.There must be twice as much vent area as the area of the fill line