Available options:
[i] Bend
[ii] strength
[iii] exercise
[iv] ligt
[v] It expands
[vi] shorten
[vii] Vibrates
[viii] stay warm
Q: Fact 1: Muscle contraction occurs when muscle fibers get shorter. Fact 2: Movement is based on the contraction of muscles. Given the two facts above, what do muscle fibers need to do to enable movement?
A:
[vi]