কোন উক্তিটি সঠিক?

A gas expands isthermally an reversibly.The work done by the gas is ______.

Two spheres $A$ and $B$ with masses in the ratio $2 : 3$ and specific heat $2 : 3$ fall freely rest. If the rest in their temperatures on reaching the ground in the ratio $1 : 2$ the ratio of their heights of fall is:-

An ideal gas $A$ and a real gas $B$ have their volumes increased from $V$ to $2V$ under isothermal conditions.The increase in internal energy