question: Q:A 63-year-old man comes to the physician for blurry vision and increased difficulty walking over the past month. He feels very fatigued after watering his garden but feels better after taking a nap. He has not had any recent illness. He has smoked one pack of cigarettes daily for 35 years. Examination shows drooping of the upper eyelids bilaterally and diminished motor strength in the upper extremities. Sensation to light touch and deep tendon reflexes are intact. An x-ray of the chest shows low lung volumes bilaterally. A drug with which of the following mechanisms of action is most appropriate for this patient?? 
  {'A': 'Inhibition of muscarinic ACh receptor', 'B': 'Regeneration of acetylcholinesterase', 'C': 'Stimulation of D2 receptors', 'D': 'Stimulation of β2 adrenergic receptors', 'E': 'Inhibition of acetylcholinesterase'},