A can't be b'coz both are dead. D can't be b'coz both conduct water. C cannot be as both have vertical row of cells. B b'coz trachieds are derived from single cell whereas vessels have originated from many file cells.

B. In being derived from a single cell

Vessels and tracheids are both types of xylem cells found in vascular plants. They are responsible for the transportation of water and minerals from the roots to the rest of the plant. However, they differ in several ways, one of which is that vessels are derived from a single cell, while tracheids are not.

What are vessels and tracheids?
- Vessels: Vessels are long cylindrical cells that are arranged end to end to form a continuous tube-like structure. They are found in angiosperms, which are flowering plants. Vessels have perforations at their ends, allowing water to flow freely between adjacent cells. This facilitates the efficient transport of water and minerals through the plant.
- Tracheids: Tracheids are also long and cylindrical cells, but they are tapered at the ends and overlap with each other. They are found in both gymnosperms (non-flowering plants) and angiosperms. Tracheids do not have perforations like vessels, so water has to pass through pits in the cell walls to move between adjacent cells.

How are vessels derived from a single cell?
Vessels are derived from a single cell through a process called vessel element formation. During this process, a single cell undergoes cell division to form a chain of cells. These cells then undergo programmed cell death, leaving behind a hollow tube-like structure that becomes the vessel. The end walls of the cells are dissolved, creating perforations that allow the flow of water.

Significance of being derived from a single cell
The fact that vessels are derived from a single cell has several implications:
- It allows for greater efficiency in water transport. The continuous tube-like structure of vessels allows for uninterrupted movement of water from the roots to the leaves.
- It enables faster water flow. The presence of perforations in vessel elements allows water to flow more freely, reducing resistance and increasing the speed of water transport.
- It allows for specialization. Being derived from a single cell allows vessels to be longer and wider than tracheids, increasing their capacity for water transport.

In conclusion, vessels differ from tracheids in that they are derived from a single cell. This structural difference has important implications for their function in water transport within plants.