The correct option is
C It conducts water and minerals efficiently
The older woody stems tend to show two distinct regions, the outer light coloured and functional sapwood (or alburnum), and the inner darker and non-functional heartwood (or duramen).
The inner zone gets dark due to progressive deposition of organic compounds like resins, gums, tannins and essential oils in vessels and tracheids of older secondary xylem (wood). These depositions result in blockage of xylary elements due to which water is not conducted.
Hence, heartwood does not conduct water and minerals but rather gives mechanical support to the stem.
The conduction of water and minerals is performed by peripherally located sapwood.
As the cells of the heartwood are dead with highly lignified walls, heartwood is hard, durable and resistant to the attacks of pests.