The correct graph between pressure $(P)$ and density $(\rho)$ of a gas at constant temperature is

$A$ gas is filled in a cylinder. Its temperature is increased by $20\%$ on the Kelvin scale and its volume is reduced by $10\%$. How much percentage of the gas must leak for the pressure to remain constant?

The air density at Mount Everest is less than that at the sea level. It is found by mountaineers that for one trip lasting a few hours,the extra oxygen needed by them corresponds to $30,000 \, cc$ at sea level (pressure $1 \, atm$,temperature $27^{\circ}C$). Assuming that the temperature around Mount Everest is $-73^{\circ}C$ and that the oxygen cylinder has a capacity of $5.2 \, L$,the pressure at which $O_2$ must be filled (at site) in the cylinder is .... $atm$.

$A$ gas has a volume of $251 \,cm^3$ at $20^{\circ} C$ and a pressure of $78 \,cm$ of $Hg$. Find its volume at $NTP$. (in $\,cm^3$)

The pressure $(P)$ and temperature $(T)$ relationship of an ideal gas obeys the equation $PT^2 = \text{constant}$. The volume expansion coefficient of the gas will be:

At $100 \, K$ and $0.1 \, \text{atm}$ pressure, the volume of helium gas is $10 \, \text{litres}$. If volume and pressure are doubled, its temperature will change to ....... $K$.