Final answer:
The smallest functional unit of a muscle is the sarcomere, making the statement that a muscle cell is the smallest functional unit false.
Step-by-step explanation:
The statement that the muscle cell is the smallest completely functional unit in the muscle is false. The smallest functional unit of a muscle is actually the sarcomere, which is a part of the muscle fiber (muscle cell). Muscle fibers themselves are composed of many myofibrils, and these myofibrils are organized into sarcomeres. The sarcomere is the basic contractile unit of striated muscle tissue and is responsible for the muscle's ability to contract and generate force.