Water Cohesion via Hydrogen Bonding in Xylem

Steps:

• Cohesion allows water molecules to stick together through hydrogen bonds, enabling upward movement in xylem as a continuous column.
• In xylem transport, this requires a linear arrangement to maintain tension without breaking.
• Examine diagrams: identify the one showing molecules in a straight chain with bonds between oxygen of one and hydrogen of another.
• Select the option matching this linear cohesion model.

Why B is correct:

• B shows four water molecules in a linear chain linked by hydrogen bonds (O-H···O), directly illustrating cohesion's role in xylem's cohesive tension per transpiration pull theory.

Why the others are wrong:

• A: Depicts scattered molecules with no bonds, failing to show cohesion.
• C: Illustrates a branched cluster, not the linear column needed for xylem ascent.
• D: Portrays a ring structure, which disrupts continuous upward flow.

Final answer: B