Which of the accompanying $PV$ diagrams best represents an isothermal process?

$Assertion :$ In an isothermal process,the whole of the heat supplied to the body is converted into internal energy.
$Reason :$ According to the first law of thermodynamics,$\Delta Q = \Delta U + P\Delta V$.

Two identical containers $A$ and $B$ with frictionless pistons contain the same ideal gas at the same temperature and the same volume $V$. The mass of the gas in $A$ is ${m_A}$ and that in $B$ is ${m_B}$. The gas in each cylinder is now allowed to expand isothermally to the same final volume $2V$. The changes in the pressure in $A$ and $B$ are found to be $\Delta P$ and $1.5 \Delta P$ respectively. Then:

During which of the following thermodynamic processes represented by a $PV$ diagram can the heat energy absorbed by the system be equal to the area under the $PV$ graph?

What is the value of the specific heat of a gas during an isothermal process?

The specific heat of a gas in an isothermal process is