Buprenorphine Is an Opioid Analgesic That Is Considered to Have $\kappa$

Buprenorphine is an opioid analgesic that is considered to have both agonist and antagonist opioid receptor effects, which allows for the benefit of providing a long duration of effect with fewer adverse effects compared to other drugs in this class. Buprenorphine exhibits agonistic activity at the ___________ receptor, and antagonistic activity at the _____________ receptor.

A) ( $\kappa$ (kappa) , $\mu$ (mu) )
B) ( $\mu$ (mu) , $\kappa$ (kappa) )
C) ( $\kappa$ (kappa) , $\delta$ (delta) )
D) (Both $\kappa$ (kappa) and $\theta$ (theta) )