Question

Which of the following statements is true?
A. Vessels are unicellular with narrow lumen
B. Vessels are multicellular with wide lumen.
C. Tracheids are unicellular with wide lumen
D. Tracheids are multicellular with narrow lumen.

Answer 1

Hint: A vessel element or vessel member is one of the cell types which are found in xylem, that is the water conducting tissue of plants. Vessel elements are typically found in flowering plants (angiosperms) but absent from most of the gymnosperms such as conifers. Tracheids are the elongated, water-conducting cell present in the xylem. Tracheids have pits where the cell wall is modified into a thin membrane, across which the water flows from one tracheid to another tracheid. The cells die when mature, leaving only their lignified cell walls.

Complete answer:
So this is a histological picture showing tracheids and vessels of plants. Vessels are multicellular having wide lumen. They are made up of a type of vessel elements that are lying one above the other. The wall of vessels is hard but not thick, having wide lumen. Whereas tracheids are unicellular with a narrow lumen.
Tracheids are known as the water-conducting and mechanical supporting cells of gymnosperms; water is transported longitudinally through endplates and laterally through pits. Angiosperm vessels function primarily to transport water and are individually shorter than tracheids .

So, the correct option is B.

Note:
The xylem tracheary elements consist of cells called as tracheids and vessel members, both of which are typically narrow, hollow, and elongated. Tracheids are less specialized than the vessel members and are the only type of water-conducting cells in most gymnosperms and seedless vascular plants.