________ is the anatomical unit of muscle.

Explanation:

1. Muscle Fibre: The muscle fibre is the anatomical unit of muscle. It is the basic building block of muscles and consists of multiple myofibrils, which are responsible for muscle contraction. These fibres are long, cylindrical cells covered by a membrane called the sarcolemma.
2. Sarcomere: While the sarcomere is the functional unit of muscle contraction, it is not the anatomical unit. Sarcomeres are the repeating units within myofibrils that enable the muscle to contract through the sliding filament mechanism.

Why Muscle Fibre is the Correct Option:

The muscle fibre is a complete structural entity that forms the muscle, whereas the sarcomere is a functional segment within it. This makes the muscle fibre the proper anatomical unit of muscle.