There are five postulates proposed by Darwin to explain the mechanism of natural selection.
- Individuals are variable (therefore, D is incorrect)
- More offspring is produced than can survive (so C is incorrect as well)
- The history of Earth is long
- Some variations are passed down (meaning that B is also wrong)
- Survival and reproduction are not random (so E is incorrect too).
The genetic drift is part of the theory of evolution proposed by Sewall Wright, not by Darwin. Therefore, the correct answer is A. Small populations can lead to genetic drift.