Natural selection causes A. changes in allele frequencies within a population. B. changes in the mechanism of inheritance. C. the inheritance of acquired characteristics. D. a decrease in reproductive fitness in a population. E. changes in an individual's genes.

Natural selection causes change in allele frequencies within a population.          

So option A is correct one.

Explanation:

Natural selection generally  work  on an organism’s phenotype, or observable features. Phenotype is often largely a product of genotype (the alleles, or gene versions, the organism carries). When a phenotype produced by certain alleles helps organisms survive and reproduce better than their peers, natural selection can increase the frequency of the helpful alleles from one generation to the next – that is, it can cause microevolution.

answer; the correct answer is conflict- related aggression; +