ANS:B - decreases

Thermal conductivity of any material is dependent on two things:

i. The motion of free electrons.
ii. Molecular vibrations.

For metals, the thermal conductivity is mainly a function of the motion of free electrons. As the temperature increases, the molecular vibrations increase (in turn decreasing the mean free path of molecules). So, they obstruct the flow of free electrons, thus reducing the conductivity.

In the case of nonmetals, there are no free electrons. So, only the molecular vibrations are responsible for conduction of heat and hence for nonmetals the conductivity increases with increase in temperature.