Cohesion-tension theory drives xylem water transport

Steps:

• Water evaporates from leaves, creating tension that pulls water upward.
• Cohesion between water molecules maintains a continuous column.
• Adhesion of water to xylem walls prevents column breakage.
• Hydrogen bonding enables both cohesion and adhesion for capillary action.

Why A is correct:

• All three properties—hydrogen bonding, cohesion, and adhesion—support the cohesion-tension mechanism, where transpiration pull relies on water's polarity for unbroken flow (as per Dixon-Joly theory).

Why the others are wrong:

• B omits adhesion, essential for water sticking to vessel walls against gravity.
• C excludes cohesion, needed for tensile strength in the water column.
• D ignores hydrogen bonding, the basis for both cohesion and adhesion in polar water molecules.

Final answer: A