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
Inotropic receptor among the following is/are: 
Select and explain. 
A. GABAa., B. Nm, C. Nn, D. All of the above.
D: All of the above.
Answer: D: All of the above. 
Explanation: Other then these NMDA and 5-HT are also inotropic receptors.