The correct answer is the last statement.
If the regulatory serine is mutated to alanine, then acetyl-CoA carboxylase will get activated spontaneously and will produce malonyl-CoA. The increased concentrations of malonyl-CoA will obstruct the oxidation of fatty acids by preventing the entry of fatty acids into the mitochondria.
It is because the AMP-activated protein kinase phosphorylates the serine residues of acetyl-CoA carboxylase to inactivate it. If a mutation occurs in such residues, then the AMPL cannot phosphorylate acetyl-CoA carboxylase and this enzyme will get activated spontaneously.
In such a situation, there will be more than sufficient production of malonyl-CoA, which will inhibit the admittance of more fatty acid getting inside the mitochondria; this will indirectly prevent the oxidation of fatty acids.
The presence of the base peak at 45 in combination with our knowledge about the nitrogen rule suggests that the peak at m/z 60 is likely the molecular ion because even molecular ions usually produce odd molecular fragments by breaking single bonds.
The insects he sprayed will die therefore leaving the predators of the insects to decrease in population
B- Electron transport chain