Step 1: Understand the concept of soil classification based on moisture content.
Soil can be classified depending on what fills its void spaces: If the voids are filled with air only, the soil is considered dry soil.
If the voids are filled with both air and water, it is partially saturated soil.
If the voids are filled with water only, it is saturated soil.
In this case, the question states that the voids contain only air, which clearly indicates dry soil.
Step 2: Analyze each option.
Dry soil: Voids are filled with air only → Matches the condition.
Partially saturated soil: Contains both air and water → Does not match.
Air entrained soil: Refers to artificially induced air bubbles in concrete or grout, not general soil classification.
Dehydrated soil: Not a standard term in soil mechanics.
Step 3: Select the correct option.
The correct classification when voids contain only air is: $$ \boxed{\text{Dry soil}} $$