Which Cells are Alive at Maturity

Question

Which cells are alive at maturity?  
A) Sieve elements
B) Vessel elements
C) Tracheids
D) Vessel elements and tracheids
E) Sieve elements and vessel elements

Accepted Answer

Sieve elements are alive at maturity, although they lack a nucleus, allowing them to function in the transport of sugars and nutrients throughout the plant. Vessel elements and tracheids, which are involved in water transport, are not alive at maturity.