Which one of these statements is FALSE?

A) The force of a muscle contraction increases as more motor units are activated.
B) Concentric isotonic contractions occur when the load equals or exceeds the tension produced in the muscle.
C) Recruitment is the process in which the number of motor units stimulated during a contraction is increased.
D) When a second stimulus occurs before the muscle has relaxed, wave summation occurs and the second contraction generates more force than the first contraction.
E) A motor unit is a motor neuron and all of the myofibers it innervates.