Answer:
D. a mutation
Explanation:
This would be called a mutation because it stated above neither of it's parents have it so say for humans both parents have 2 arms which is normal. They have a child and he/she only has one arm thus mutation.
Skeletal muscle support and Movement. Skeletal muscles move the body. Skeletal muscle contractions pull on tendons, which are attached to bones. If contraction of the muscle causes the muscle to shorten, the bone and, thus, the body part will move.
so your answer is D
