What relationship exists between changes in the environment and variation?

Changes in the environment cannot influence the fitness of an organism.
Changes in the environment cannot change which traits are advantageous
Changes in the environment can act only on existing variations in a population.
Changes in the environment can only cause new variation to appear.

Changes in the environment can act only on existing variations in a population. By selecting for certain traits in response to environmental changes, natural selection can lead to an increase in the frequency of certain variations within a population. This can ultimately result in changes in the overall genetic makeup of a population over time.

so what's the answer from the choices listed