Joaquin's doctor tested Joaquin's reflexes by tapping his knee. The doctor
explained to Joaquin that the tapping sends a signal to his spinal cord. The
spinal cord then sends a signal to the muscle in Joaquin's thigh, and his leg
moves. Which of the following body systems is involved in this process?
A. Respiratory system
B. Nervous system
C. Skeletal system
D. Digestive system​