This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
Which of the following adrenergic receptors are metabotropic receptors? 
Select and explain. 
A. Alpha 1, B. Alpha 2, C. Beta 1, D. All the above
D: All the above
Answer: D: All the above 
Explanation: All adrenergic receptors are GPCR or metabotropic receptors.