Answer:
c) Organisms within a population vary, and all populations produce more offspring than can be supported by the environment, resulting in competition for survival within the population.
Explanation:
Darwin's theory was based on the evidence of natural selection and survival of the fittest.
Evidence of Darwin's theory were observed from the variation in the population which is supported by the environmental factor (natural selection) and these population than produce offspring, resulting in competition for survival within the population (survival for fittest).
Hence, the correct option is "c".