This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Physiology
Posture is maintained by 
Select and explain. 
A. Crossed extensor reflex, B. Stretch reflex, C. Golgi tendon reflex, D. None
B: Stretch reflex
Answer: B: Stretch reflex 
Explanation: The dynamic stretch reflex is elicited by the potent dynamic signal transmitted from the primary sensory endings of the muscle spindles, caused by rapid stretch or unstretch. Thus when a muscle is stretched or unstretched, a strong signal is transmitted to the spinal cord which causes an instantaneous strong reflex contraction(or decrease in contraction) of the same muscle from which the signal originated. Thus, reflex functions to oppose sudden changes in muscle length, which maintains the posture. REF: TEXTBOOK OF MEDICAL PHYSIOLOGY GUYTON AND HALL, 12e Page no 771