2 - Human refuse to stop polluting.
All other three are attempting to attack the problem of pollution.
Answer:
Gamma-aminobutyric acid (GABA)
Explanation:
Gamma-aminobutyric acid (GABA) is the inhibitory neurotransmitter found in the central nervous system of mammals, especially humans, which is responsible for the regulation of communication between the brain cells, and also implicated in the slowing down of signals as neuronal impulses is reduced when it is activated. This is mostly responsible for the extreme uninhibited behaviors often associated with large alcohol consumption.
