The knee jerk reflex in response to a mallet tap over the patellar ligament
A. Is a conditional reflex
B. Is a monosynaptic reflex
C. Has its reflex centre in the spinal cord
D. Is mediated by a three neuron reflex are

Hint: Knee jerk reflex in which knee jerk is the involuntary response of the body, in response to a powerful tap on the patellar ligament, which lies just below the knee cap. Sudden kicking off the leg in response to a mallet tap over the patella ligament is known as knee jerk reflex.

Step by step answer:When a sudden strike of a mallet taps over the patellar ligament this stimulates impulses in the afferent neuron which carries impulses to the spinal cord via dorsal nerve root. In the gray matter of the spinal cord interneurons present which form connections between afferent neurons and efferent neurons. Interneurons form synapses between the sensory neurons and motor neurons. In knee jerk reflex single synapse is formed between sensory neurons(afferent) and motor neurons(efferent) pathways. This type of reflex is known as a monosynaptic reflex. The knee jerk reflex in response to a mallet tap over the patellar ligament is a monosynaptic reflex.
So, the correct option is (B)
Additional Information: Reflexes can be of many types.
-Conditional reflex: Acquired after birth through learning or conditioning. Example-saliva after seeing favorite food, playing musical instruments.
-Unconditional reflex: Inborn reflexes are called unconditional reflexes. Example-knee jerk, peristalsis.

Note: Reflexes according to number of synapses:
1. Monosynaptic reflex: When only one synapse forms in the reflex path.
2. Polysynaptic reflex: When more than one synapse is formed in the reflex path.