Answer:
C. After many generations, the offspring of the introduced guppies with mature at an older age and larger size because of selective pressure from the new predator.
Step-by-step explanation:
In the above scenario evolutionary biologists found variation in guppies with average age and size due to selective pressure from the predators including pike cichlids and killifish. As cichlids preys larger guppies primarily and killifish preys smaller guppies but with killifish, it has been found that guppies reproduced at older age and larger at maturity.
So, because of selective pressure, the new generation of guppies will be mature at an older age with increase in size.