Answer : The correct answer is -
b. a negative feedback.
Negative feedback is a mechanism of regulation for physiological functioning in the living systems.
It causes decline /reduction in the response by a particular stimulus.
As per the question, the production of nerve (through sprouting factor) causes it to release anti sprouting factor, which leads to the inhibition of nerve growth.
In other words, the stimulus anti sprouting factor (released by nerve) causes the decline of nerve growth.
Thus, it is an example of negative feedback.
