Why is a higher moisture content permitted for crushed roofing slag compared to crushed stone and gravel?

The correct answer highlights that a higher moisture content is permitted for crushed roofing slag due to the moisture entrapment in the internal pores of the pieces of slag. This characteristic is important because crushed roofing slag is typically more porous than other materials like crushed stone and gravel. The internal structure of slag allows it to retain moisture without adversely affecting its performance in roofing applications. This moisture retention can help improve the adhesion characteristics of the roofing system, providing better overall performance when used as a surfacing material.

While the other options might seem plausible, they do not accurately relate to the properties of crushed roofing slag. Enhancing the weight of the material, improving overall durability, or allowing for a smoother application process are not inherent characteristics linked to the moisture content of the materials involved in the same way that moisture entrapment is directly tied to the physical structure of roofing slag.