I think the answer is nitrogen fixation.
Autoinducer molecules are signalling molecules that need bacteria. In order for the autoinducer molecules to signal, the bacteria must find a way to initiate the signal and a way to respond to the signal it had created. Autoinducer molecules increase in production as the density of the bacteria cell increases.
Any place where there are living organisms
The answer is c I did this like 2 days ago