A stone is rejected if it absorbs water more than A. 5% B. 10% C. 15% D. 20%

The correct answer is A. 5%.

A stone is rejected if it absorbs water more than 5% because it is considered to be too porous. A porous stone will not be able to hold up to the weight of a building and is therefore not safe to use.

Option B, 10%, is incorrect because it is not the standard for rejecting stones. Option C, 15%, is incorrect because it is not the standard for rejecting stones. Option D, 20%, is incorrect because it is not the standard for rejecting stones.

The standard for rejecting stones is 5%. This means that if a stone absorbs more than 5% of its weight in water, it is considered to be too porous and will be rejected.