This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
The principal central action of caffeine is on the: 
Select and explain. 
A. Cerebral cortex, B. Corpus callosum, C. Hypothalamus, D. Spinal cord
A: Cerebral cortex
Answer: A: Cerebral cortex 
Explanation: None