Root hairs' absorption mechanisms for water and ions

Steps:

• Root hairs extend from root epidermis to maximize soil contact for nutrient uptake.
• Water enters root hairs passively along a water potential gradient.
• Mineral ions enter against their concentration gradient using cellular energy.
• Compare options to biological processes of osmosis (passive water movement) and active transport (energy-requiring solute movement).

Why D is correct:

• Osmosis defines water movement across semi-permeable membranes from higher to lower water potential without energy input.

Why the others are wrong:

• A: Ions move against gradients via active transport, not osmosis.
• B: Water follows passive osmosis, not energy-dependent active transport.
• C: Ion uptake uses active transport, but root hairs' key role is water absorption by osmosis.

Final answer: D