The correct answer is: C. Permeability.
Pozzolana is a siliceous or siliceous and aluminous material that in itself possesses little or no cementitious value but in finely divided form and in the presence of water, reacts chemically with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties.
The addition of pozzolana to ordinary Portland cement increases the impermeability of the concrete. This is because pozzolana reacts with calcium hydroxide to form calcium silicate hydrate (C-S-H), which is a very dense and impermeable material.
Bleeding is the upward movement of water and cement paste to the surface of concrete during or shortly after placing. Shrinkage is the decrease in volume of concrete that occurs after it has been placed and hardened. Heat of hydration is the heat that is generated when cement reacts with water.
The addition of pozzolana to ordinary Portland cement can reduce bleeding and shrinkage. This is because pozzolana reacts with calcium hydroxide to form C-S-H, which is a very dense and impermeable material. C-S-H also has a lower heat of hydration than calcium silicate hydrate (C-S-H), which is the main hydration product of Portland cement.