Answer: B.) High specific heat capacity
Explanation:
Thermal insulators are materials that are bad conductors of thermal energy.
On the other hand, the specific heat capacity of a material is defined as the amount of heat needed to raise the temperature of 1 kg of the material by 1K.
So:
If a material has a low specific heat capacity, it means that it takes a short time to absorb the heat, hence a temperature increase occurs shortly. These are excellent thermal conductors.
But if a material has high specific heat capacity, it will take longer to absorb heat and is therefore an excellent thermal insulator.