A reflex arc MUST consist of all the following EXCEPT:Question 16Answera.Spinal cordb.An afferent nerve fibrec.A sensory receptord.An effectore.An efferent nerve fibre

The question is asking which component is not a necessary part of a reflex arc.

A reflex arc is a neural pathway that controls a reflex action. In its simplest form, a reflex arc consists of the following components:

a. Sensory receptor: This is the structure that detects changes in the environment (stimuli).

b. Afferent nerve fibre: This is the nerve fibre that transmits signals from the sensory receptor to the central nervous system.

c. Spinal cord: This is part of the central nervous system where the signal from the afferent nerve fibre is processed.

d. Efferent nerve fibre: This is the nerve fibre that transmits signals from the central nervous system to the effector.

e. Effector: This is the structure (usually a muscle or gland) that performs the action in response to the signal from the efferent nerve fibre.

Therefore, all of the components listed (a-e) are necessary for a reflex arc. The question seems to be incorrect as it states that one of these is not necessary.