The correct option is
A Dead at maturity
Vessel elements are the cells that form vessels, a water conducting element in angiosperms. It is a type of xylem tissue. Vessels are not found in gymnosperms where the water conduction occurs by means of tracheids. Due to the presence of vessels, the angiosperm wood is called porous wood because the vessel elements have wider lumen. These cells lose their cytoplasm at the maturity due to the deposition of lignin in their walls. So, these are dead cells.
Hence, the correct answer is 'Dead at maturity'