Water vapor exits leaves via passive diffusion in transpiration

Steps:

• Identify the process: Water vapor passes out of leaves through stomata during transpiration.
• Recall key mechanism: Transpiration involves the movement of water molecules from high concentration inside the leaf to lower concentration in the air.
• Match to options: This passive movement without energy input aligns with diffusion, not energy-requiring or specialized transport.
• Eliminate mismatches: Rule out active processes or those for solutes/sugars.

Why B is correct:

• Diffusion is the net movement of particles from high to low concentration areas, as defined by Fick's law, matching water vapor's passive exit through stomata.

Why the others are wrong:

• A: Active transport uses energy to move substances against concentration gradients, but transpiration is passive.
• C: Osmosis involves water diffusion across semi-permeable membranes, not vapor in air.
• D: Translocation moves sugars via phloem, unrelated to water vapor loss.

Final answer: B