By Which Mechanism Does Lubiprostone Relieve Some Cases of Severe

By which mechanism does lubiprostone relieve some cases of severe idiopathic constipation?

A) blockade of serotonin 5-HT₃ receptors
B) activation of serotonin 5-HT₄ receptors
C) inhibition of fluid reabsorption in the colon
D) stimulation of the parasympathetic nervous system
E) activation of chloride channels