Water absorbed by roots is transported to leaves through xylem vessels — a network of tube-like structures running from roots through the stem to leaves. This upward movement occurs due to transpiration pull: water evaporates from leaves through stomata, creating a suction force that pulls water continuously upward through the xylem.
The examiner expects two key points: (1) the tissue responsible — xylem, and (2) the driving force — transpiration pull (loss of water vapour through stomata creates suction). Both points are needed for full marks. Avoid vague terms like "absorbed by stem"; be specific about the mechanism.