Which of the following is an example of natural selection?
a. pesticides are sprayed in a field, resulting in an increase in crop growth and a decrease in insect population.
b. cricket frogs prefer to sleep during the day, while red-eyed tree frogs prefer to sleep during the night.
c. rabbits with a mutation for longer, thicker fur survive an unusually cold winter, while many normal rabbits do not survive.
d. to produce a more desirable fruit, a farmer crosses a tree that produces sweet oranges with a tree that produces large oranges.