The best response to the question based on the provided information is:
a. Before the layers touch, the outer layer is hotter than the inner layer. Once the layers are touching, the outer layer will transfer kinetic energy to the molecules in the cooler inner layer until both layers reach the same temperature, which will be in between their starting temperatures.
This option accurately describes the temperature difference between the two layers before they touch and correctly explains the process of thermal equilibrium, where energy is transferred from the higher-energy molecules in the outer layer to the lower-energy molecules in the inner layer until they reach a common temperature.