The internal energy of an ideal gas increases during an isothermal process when the gas is

An ideal gas undergoes a cyclic transformation starting from the point $A$ and coming back to the same point by tracing the path $A$ $\rightarrow B$ $\rightarrow C$ $\rightarrow D$ $\rightarrow A$ as shown in the three cases above. Choose the correct option regarding $\Delta U$.

Which of the following transformations is endothermic in nature?

An ideal gas is compressed from $10 \ dm^3$ to $1 \ dm^3$ at a constant pressure of $2 \ bar$. Calculate the work done on the gas during compression. (in $kJ$)

The maximum work done in expanding $16 \, g$ of $O_2$ gas isothermally at $300 \, K$ from an initial volume of $5 \, dm^3$ to a final volume of $25 \, dm^3$ is:

$1.0 \ mol$ of a monoatomic ideal gas is expanded from state $(1)$ to state $(2)$ as shown in the figure. Calculate the work done for the expansion of the gas from state $(1)$ to state $(2)$ at $298 \ K$.