The atmospheric pressure at earth surface is $P_1$ and inside a mine is $P_2$. They are related as :
(a) $P_1=P_2$

(b) $P_1>P_2$
(c) $P_1<P_2$

(d) $P_2=0$

The pressure $P_1$ at a certain depth in river water and $P_2$ at the same depth in sea water are related as:

The pressure P1 at the top a dam and P2 at a depth h from the top inside water are related as:

V verus T curves at constant pressures $P_1$ and $P_2$ for an idealgas are shown in the figure,