The correct answer is root hairs
Reason -
The roots hairs are most important in the process of water absorption through soil as the root hairs are the basic contact point through which root connects to the soil. The root hairs increases the surface area of roots for contacting the soil and there by reduces the distance through which ions or water need to travel to reach the root surfaces. Root hairs being thin are capable to penetrate into deep soils which further is an added advantage.