Which event describes a change where evolution has happened?

Missing choices:
A) An allele frequency changes in a population
B) A school of fish moves to a new environment
C) A species of fish dies out

My
A) An allele frequency changes in a population.

Important factors affecting allele frequencies are Genetic Isolation, Migratio, Mutation, Natural Selection, Artificial Selection, and Chance.

This would be a example of a "i want to be single person"