The correct option is (a) (T∞-T)\(\frac{h}{k}\)

For explanation: Let Tx be temperature gradient developed at the surface. If the heat transfer coefficient at the surfaces of a wall is assumed to be h units, then the heat interaction at the surfaces of the wall is evaluated by Equating the conduction heat transfer to the convection heat transfer, i.e.,

kATx = hA(T-T∞)

Tx=(T∞-T)\(\frac{h}{k}\).