Answer : 3. "When there is no selective pressure"
Explanation :

Answer: C) When there is no selective pressure Explanation: Genetic drift or allelic drift is the change in the relative frequency in which a gene variant (allele) occurs in a population due to random sampling and chance.   When is genetic drift a major factor in evolution is * When there is low gene flow. * When there is no selective pressure. * When there is a bottleneck.