Genetic drift occurs in small scale, but mutation occurs in large population.

Explanation:

Random genetic drift is a mechanism of evolution that occurs when there is a change in the frequency of a gene variant (allele) in a population due to random sampling. It is more likely to occur in small populations, and this is why the correct answer is option 'A'.

Small population size:
When a population is small, the number of individuals carrying a specific allele is also small. As a result, there is a higher chance of random fluctuations in allele frequencies from one generation to the next. In other words, random genetic drift has a greater impact on small populations because there is less genetic diversity and fewer individuals to contribute to the gene pool.

Explanation in detail

Highly genetically variable individuals:
Although genetic variability can influence the rate of evolution, it does not directly result in random genetic drift. Genetic variability refers to the presence of different alleles within a population. While it can contribute to the overall genetic diversity of a population, it does not necessarily lead to random changes in allele frequencies over time.

Interbreeding within this population:
Interbreeding within a population can affect genetic diversity and the potential for random genetic drift, but it does not directly cause it. Interbreeding can lead to the exchange of alleles between individuals, which can increase the overall genetic variability of a population. However, the occurrence of random genetic drift is more closely associated with the size of the population rather than its interbreeding patterns.

Constant low mutation rate:
A constant low mutation rate does not directly lead to random genetic drift. Mutation is a source of genetic variation in a population, but its impact on allele frequencies is dependent on other factors such as population size and the strength of selection. Random genetic drift is specifically associated with random changes in allele frequencies due to sampling effects, rather than the introduction of new alleles through mutation.

In conclusion, random genetic drift is more likely to occur in small populations due to the increased probability of random fluctuations in allele frequencies. While factors such as genetic variability, interbreeding, and mutation can influence the overall genetic diversity of a population, they do not directly result in random genetic drift.