This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Pharmacology
Buprenorphine partial agonist at which opioid receptor? 
Select and explain. 
A. Mu, B. Kappa, C. Delta, D. Lambda
A: Mu
Answer: A: Mu 
Explanation: Ans. is 'a' i.e., Mu o Buprenorphine is partial agonist on mu receptor and antagonist at Kappa receptor.Nature of interaction of opioid ligands with the three major types of opioid receptors, along with equivalent analgesic dosesLigandm (mu)k (kappa)d (delta)Analgesic dose (mg)1. MorphineAgo. (St)Ago. (W)Ago. (W)102. NalorphineAnta. (St)Ago. (M)--3. PentazocineP. Ago., Anta. (W)Ago. ( M)-30-604. ButorphanolP. Ago. (W)Ago. (St)-1-35. BuprenorphineP. Ago.Anta. (M)-0-3-046. NaloxoneAnta. (St)Anta. (M)Anta. (W)-7. NaltrexoneAnta. (St)Anta. (M)Anta. (W)_8. Met/Leu enkephalinAgo. (M)-Ago. (St)_9. (3-EndorphinAgo. (St)-Ago. (St)_10. Dynorphin A, BAgo. (W)Ago. (St)Ago. (W)-