Which of the Following Is NOT a Correct Pairing of Structure

Which of the following is NOT a correct pairing of structure and function?

A) motor endplate: region of the motor neuron axon that releases acetylcholine
B) sarcoplasmic reticulum: modified endoplasmic reticulum that stores Ca²⁺
C) T-tubules: infoldings of the plasma membrane that conduct electrical signals deep into the muscle fiber
D) troponin: protein that moves tropomyosin when activated by Ca²⁺
E) tropomyosin: protein that lies between the helices in actin and blocks myosin-binding sites when the muscle is at rest