The second Option is correct i.e
- Because it is unsaturated.
By definition, the zone of aeration is layer of Earth where the pores and cracks are filled with air and water. It is sub-earthen region that exists between the Earth's surface and water table. This zone mainly comprises porous soil & rock. The pores in this layer are usually partially filled with water, while rest of them are filled with air. Thus, in this layer, air and water are able to interact with each other, leading to aeration of water. Therefore, this zone is known as zone of aeration.