Answer:
b. the contractile unit between two Z discs
Explanation:
A sarcomere is the functional and mechanical unit of striated muscle structure, is formed of thin filaments (two strands of actin and one strand of regulatory protein) and thick filaments (myosin). They have the ability to contract in unison coordinating the muscles’ contractions. As you can see in the image added these units are located between Z discs.
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