QUESTION 15 Which of the following statements applies best to the term 'receptor reserve?

Receptor reserve is determined by the number of receptors that are required to be occupied by agonist to initiate a
maximal response compared to the total number of cell-surface receptors.
Receptor reserve, also known as 'spare receptors', occurs when the Kd for agonist binding to the receptor is smaller
than the EC50 determined for a particular physiological response.
Receptor reserve is a useful pharmacological parameter, as it is specific to a particular cell-type.
Receptor reserve refers to the pool of intracellular receptors that are able to translocate to the plasma membrane.