What is the function of the sarcomere?

I - The sarcomere is responsible for the contractility of muscle fibers.
II - The sarcomere is responsible for the connection between a motor neuron and a muscle fiber.
III - The sarcomere is responsible for the transmission of impulses between neurons.
IV - The sarcomere is responsible for the production of neurotransmitters.
a) Only I is correct.
b) I and II are correct.
c) I and III are correct.
d) I and IV are correct.