A first class brick when immersed in cold water for 24 hours should not absorb water more than

Answer: Option B

A first-class brick is characterized by its high quality and durability.

It is required that when such a brick is immersed in cold water for 24 hours, it should not absorb water more than 20% of its dry weight.

This specification ensures the brick has good strength and resistance to weathering.

Hence, the correct answer is Option B: 20%.