Which relation is correct for the given $P-V$ diagram?

$A$ cylindrical tube of cross-sectional area $A$ has two airtight,frictionless pistons at its two ends. The pistons are tied with a straight piece of metallic wire. The tube contains a gas at atmospheric pressure $P_0$ and temperature $T_0$. If the temperature of the gas is doubled,then the tension in the wire is:

$A$ $20 \,cm$ long tube is closed at one end. It is held vertically,and its open end is dipped in water until only half of it is outside the water surface. Consequently,water rises in it by height $h$ as shown in the figure. The value of $h$ is closest to (assume that the temperature remains constant,$P_{\text{atm}} = 10^5 \,N/m^2$,density of water $\rho = 10^3 \,kg/m^3$,and acceleration due to gravity $g = 10 \,m/s^2$): (in $,cm$)

The perfect gas equation for $4 \ g$ of hydrogen gas is

If the pressure of a gas contained in a closed vessel is increased by $0.4\%$ when heated by $1\,^{\circ}C$,the initial temperature must be

$Assertion :$ One mole of any substance at any temperature or volume always contains $6.02 \times 10^{23}$ molecules.
$Reason :$ One mole of a substance always refers to $S.T.P.$ conditions.