Agonists bind to and antagonists bind to receptors; nothing, since they do not bind receptors; receptors receptors; the cell membrane the cell membrane; receptors

Option B, receptors receptors

Explanation:

Both the Agonists and antagonists binds to the receptors.

An agonist is a form of chemical that binds to a receptor site in order to activate the receptor and produce some biological responses or action.

An antagonists is also known as a blocker and is intended to block the action potential of agonist. An antagonists is also a form of receptor ligand or drug which reduces or slow downs the effect of an agonist.  

Hence, option B is correct

d we did this already