How are these homologous structures evidence of an evolutionary relationship?

Which of the following examples can cause gene flow between populations? a.an increase in predators to a population of zebra b.a volcanic eruption that kills half of a population of mice c.bird droppings that contain seeds from a different location d.a person that sprays a toxin on a group of mosquitoes

9. the history of life on earth is recorded in

This is a situation in which genes are attached to an organism's sex chromosomes; the sex of an organism influences the expression of a gene.