Question

what are muscle fibers?
small sacs present in the lungs that help in respiration.
cylindrical cells that are capable of contracting and relaxing.
a type of bacteria found in the human digestive system.
thin strands of hair - like structures present in the body.
a type of connective tissue that helps in joining bones together.

Explanation:

Muscle fibers are cylindrical cells that can contract and relax to enable movement. The other options describe different biological structures or organisms not related to muscle fibers.

Answer:

B. Cylindrical cells that are capable of contracting and relaxing.