In an isothermal process, the temperature remains constant. The internal energy of an ideal gas is a state function that depends on temperature. Hence, change in internal energy is zero and from the first law of thermodynamics: ΔU = Q - W, where ΔU = change in internal energy, Q = amount of heat given and W = work done by it.

Since ΔU = 0 in this case, we get Q = W.

Options (a) and (b) are incorrect because we actually provide a finite amount of heat to the system, and hence work is also not zero.

Option (c) is incorrect because we just showed that Q = W.

Hence, the correct option is option (d).