Muscle contraction occurs when muscle fibers get shorter.
Muscles are bundles of fibers that can contract.
Bundles of fibers contraction occurs when bundles of fibers get shorter. .
What contracts as it gets shorter?

[A] layers of fat
[B] Epidermis
[C] Veins and arteries.
[D] Shortstop
[E] Labor
[F] Contracts
[G] the body's largest organ
[H] Bundles of fibers