Correct Answer - B
The vaetical conduction fo wter from root to aerial parts of plant is called ascent of sap. The water molecules remain joined to each other due to a force of attraction called cohesion force. This atraction is due to the presence of hydrogen bonds between them.
The magnitude of this force is vey high therefore, continuous water column in the cylem cannot be broken easily due to the force of grvity or other obstructions offered by internal tissues in the upward mvement of water. This adhesive property of water i.e., attraction between the water molecules and the walls of xylem also ensures the continiuity of water column in xylem.