a) Increase in volume of sand due to moisture absorption
b) Increase in weight of sand due to moisture absorption

c) Increase in mass of sand due to moisture absorption

d) Increase in strength of sand due to moisture absorption

Answer: a
Explanation: When water is added to sand, a thin film of water is formed around the sand particles. The film exerts surface tension on particles, making them move apart. This leads to an increase in volume because there is no direct contact among particles.