Heartwood differs from sapwood in (a) presence of rays and fibres

Correct option (c) having dead and non-conducting elements

Explanation

As a result of continued secondary growth in subsequent years, the older part of secondary xylem or wood becomes non-functional (dead) as it loses the power of conduction. The cells of this wood are filled with resins or tannins produced by adjacent functional cells. The activities of vessels become blocked by tyloses. Due to these activities, non-functional, secondary xylem becomes hard, durable and blackish in colour, called hreartwood. Now, the function of secondary xylem (water and mineral conduction from roots) is performed by outer younger-rings of xylem which is called sapwood.