Final answer:
The size of motor units can vary and is not directly related to the precision of movements. The fewer muscle fibers stimulated by a motor neuron, the more precise the movements of that muscle can be.
Step-by-step explanation:
Motor units consist of a motor neuron and the muscle fibers it controls. The size of motor units can vary, with some containing only a few dozen muscle fibers and others containing a few thousand. The statement that is incorrect about motor units is c. The more muscle fibers stimulated by a motor neuron, the more precise the movements of that muscle can be. In reality, the opposite is true: the fewer muscle fibers stimulated by a motor neuron, the more precise the movements of that muscle can be.