How do mutations occur? a. Mutations occur through the intentional alteration of amino acids.
b. Mutations occur as directed responses to changes in the environment.
c. Mutations occur through a negative change within that organism's DNA
d. Mutations occur randomly through changes in DNA.

D - Mutations occur randomly through changes in DNA.

Explanation:

Mutations can result from DNA copying mistakes made during cell division, exposure to ionizing radiation, exposure to chemicals called mutagens, or infection by viruses. Germ line mutations occur in the eggs and sperm and can be passed on to offspring, while somatic mutations occur in body cells and are not passed on.

fumikage isn't really a bird, and tsuyu does have teeth. tsuyu has a transformation quirk which still allows her to be partially human. otherwise we'd have a large frog running around. fumikage has teeth because again, he isn't a bird. his head was a quirk mixture if i'm correct.