Marshall made the following table to compare the functions of physical structures in plants and animals:


Function Animal Structure Plant Structure
Provides support for the organism Skeleton
Exoskeleton Stem
Reproductive organs Testes
Ovaries Stamen
Pistil
X Skin
Fur
Feathers Waxy Covering
Bark


Which of the following should replace X?
Protect the internal organs of the organism
Protect the organism from harsh conditions
Transports water throughout the organism
Involved in reproduction of the organism