Modeling Experiments on Walking and Swimming in Robotic Salamanders Suggest

Modeling experiments on walking and swimming in robotic salamanders suggest that

A) each type of repetitive motion that an animal performs is controlled by a distinct central pattern generator.
B) some repetitive motions are controlled by a central pattern generator, but others are not.
C) a particular central pattern generator always produces the same pattern of limb movements.
D) simple changes in the coordination of central pattern generators can produce different locomotor gait.