Final answer:
The monsynaptic stretch reflex is not involved in controlling posture. Postural control requires coordination of various muscles and reflexes. Therefore, the given statement is False i.e B.
Step-by-step explanation:
The main manifestation of the monosynaptic stretch reflex is an abrupt, involuntary contraction of a muscle in reaction to a stretch or lengthening. This reflex arc is a fast and natural way to keep muscles in check and avoid overstretching. It involves a single synapse between a sensory and a motor neuron in the spinal cord.
Although it contributes to the preservation of muscle and joint stability, it is not the principal system that regulates posture as a whole. A more intricate and coordinated process, posture is the result of the integration of several reflexes, sensory information, and higher brain centres' control over the central nervous system.
Therefore, the given statement is False i.e B.