The process of seeping of water into the ground is called _______.

Infiltration

The correct answer is option 1. Infiltration.

Here's why:

1. Infiltration specifically refers to the process of water entering the ground through cracks, pores, and spaces in the soil and rock.
2. Soaking is a more general term that can refer to any process of liquid being absorbed into a material, not just the ground.
3. Percolation describes the movement of water through a porous material, which can happen after infiltration.
4. Filtration involves the separation of suspended particles from a liquid, which is not the primary function of infiltration.

Therefore, infiltration is the most accurate term for the process of water seeping into the ground.