Step-by-step explanation:
Root hair cells are used in plants to absorb water and minerals so the plant can survive.
To do this they need a large surface area, so as much of these subjects can move into the plant as possible.
Therefore, root hair cells have many tiny root hairs, which massively increase the surface area of each root hair cell and enable it to efficiently take in water and minerals.
Hope this helps! Let me know if you have any questions or would like anything further explained :)