The pressure in the air space above an oil (sp. gr. 0.8) surface in a tank is 0.1 kg/cm". The pressure at 2.5 m below the oil surface will be
A. 2 metres of water column
B. 3 metres of water column
C. 3.5 metres of water column
D. 4 m of water column
Answer: Option B

Explanation
Psurface of oil column+row(oil)*g*h(below the oil surface)=row(water)*g*H(water column Lenth)
.1*10000*9.81+800*9.81*2.5=1000*9.81*H (Kg/cm2 convert to Kg/m2 so that multiple 10000)
H=3m