To expand on this, organophosphates are commonly used as insecticides, and function by binding acetylcholinesterase and "deactivating" it, so to speak. This results in an excess of ACh within the synapse, which causes sludge syndrome (vomiting, sweating, diarrhea -- basically lots of fluids). The treatment for this is typically atropine (antimuscarininic), and pralidoxime (if given early enough, can "reactivate" the ACh-ases). The diagram given does not show ACh-ase, only the ACh-R, therefore D is the best answer.
Organophosphate poisoning = Antidote = Atropine (Airway M receptor blocker) = dilation of bronchioles