The function of the root hair in plants is to

Step 1: Analyze the question The question asks about the main function of root hairs. These are tiny, thin extensions of the epidermal cells of the root, found just behind the root tip.

Step 2: Explain the concept Root hairs greatly increase the surface area of the root in contact with the soil. They are thin-walled and have a large vacuole containing cell sap, which is a more concentrated solution than the soil water around it. They are specialized for:

• Absorbing water from the soil by osmosis, because water moves from the soil, where it is dilute, into the root hair cell, where the sap is more concentrated, through a partially permeable membrane.
• Absorbing mineral salts by diffusion and active transport.

Step 3: Evaluate each option

• A. Absorb soil water by the process of osmosis. Correct. This is the main function of root hairs.
• B. Excrete water and mineral salts by simple diffusion. Wrong. Root hairs take in water and salts. They do not excrete them.
• C. Purify the soil for the plant. Wrong. Plants do not purify soil through root hairs.
• D. Translocate manufactured food. Wrong. Translocation of manufactured food (sugars) is done by the phloem, not the root hairs.

Step 4: Answer The correct option is A.

Tip: Remember "Root hair = Water in." Root hairs bring in water and salts, xylem carries water up, and phloem carries food around. If an option says root hairs "excrete" or "translocate food", eliminate it immediately.