During which thermodynamic process does $T$ remain constant, while the other two variables $P$ and $V$ change?

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

$A$ poly-atomic molecule $(C_v = 3R, C_p = 4R$,where $R$ is the gas constant) goes from phase space point $A (P_A = 10^5 \ Pa, V_A = 4 \times 10^{-6} \ m^3)$ to point $B (P_B = 5 \times 10^4 \ Pa, V_B = 6 \times 10^{-6} \ m^3)$ and then to point $C (P_C = 10^4 \ Pa, V_C = 8 \times 10^{-6} \ m^3)$. The path $A$ to $B$ is adiabatic and the path $B$ to $C$ is isothermal. The net heat absorbed per unit mole by the system is:

If the pressure of an ideal gas is decreased by $10 \%$ isothermally,then its volume will

In isothermal expansion,the pressure is determined by

The condition $dQ = dW$ holds good in which of the following?