The correct option is D Persistent bracts
The small projections present on the surface of pineapple fruit represent persistent bracts. Pineapple is a sorosis fruit that develops from spike or spadix or catkin where the juicy and fleshy part is formed from the axis, the bract and the perianth.
Flowers with bracts-reduced leaf found at the base of the pedicel - are called bracteates and those without bracts, ebracteate. Bracts are specialized plant structures that serve varied functions such as attracting pollinators and protecting inflorescences (flower structures).
Hence, option D is correct.