This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cell Membrane and transpo protiens, Subject name: Physiology
Which one the following does NOT primarily involve an action K+ channels? 
Select and explain. 
A. Hypoxic Pulmonary Vasoconstriction, B. Insulin secretion by Sulfonylurea, C. Carotid body discharge with reduced O2, D. Dantrolene in the treatment of Malignant Hypehermia
D: Dantrolene in the treatment of Malignant Hypehermia
Answer: D: Dantrolene in the treatment of Malignant Hypehermia 
Explanation: Hypoxic pulmonary vasoconstriction and carotid body discharge are brought about by the O2-sensitive K+ channel. Insulin secretion by sulfonylurea is brought about by its action the ATP-sensitive K+ channel on the pancreatic b-cell. Malignant hypehermia is a disorder of excitation-contraction coupling, resulting from genetic defect of RyR (a Ca++-release channel). Dantrolene uncouples the excitation from contraction, by acting on the Ca++ channel.