Answer:
The correct answer is - d. gradualism.
Explanation:
Gradualism is a model of evolution that explains that the smaller variation in an individual organism that is occurring over a period of the time is to the betterment of the organism in their environment.
These changes or variations allow them to thrive and survive with a slow successive change in an evolutionary line or the whole population. It is a consistent process.
Thus, the correct answer is - D. gradualism.