The expression for the work done for a reversible polytropic process can be used to obtain the expression for work done for all processes, except reversible __________ process.

Answer: Option B

For a polytrophic process we know $$P{V}^n=\text{constant}$$
So, the work done in an polytrophic process is $$W=\frac{P_2{V}_2-P_1{V}_1}{n-1}$$
So, we can see clearly when $$n=1$$  the work done is becoming infinity which is wrong conceptually hence the above formulae can’t be applied in case of isothermal $$\left(n-1\right)$$  process.