Answer:
a) True
Explanation:
When two bodies at different temperatures (in this case the potato and the oven), get in touch each other, thre exists a heat transfer from the body at the higher temperature to the one with lower temperature, until both reach to a same temperature, state which is known as thermal equilibrium.
We assume for simplicity, that the oven is perfectly adiabatic, so it can't exchange heat with anything outside.