Answer: Option C. "disperse seeds"
Step-by-step explanation:
Fruits are evolved from the dispersion of seeds which are formed from ovules present in the ovary.
Seed dispersal can be defined as the movement or transfer of seeds away from the parent plant.
There are several ways of seed dispersal that supports evolution of fruit including by animals, birds , insects, wind and water. Animals went to plants for the purpose or food and some seed get stick to their body which helps in seed dispersal to other places, Birds and insects get attracted to the appearance of flowers and carry seeds or some pollen with them and spread on other flowers, wind transport seed along with it and plants near a river or water surface uses the flowing water to transport their seeds.
Hence, the primary structure responsible for fruit is disperse seed.