Change the Underlined Words So That the Sentence in Italics

Change the underlined words so that the sentence in italics is consistent with Dale's principle. Select the best words below to replace the underlined section. Neurons may contain several types of neurotransmitters. Each synapse uses different combinations of neurotransmitters at each synapse to communicate with post-synaptic cells.

A) nitric oxide and one other neurotransmitter
B) the same combination of neurotransmitters
C) both excitatory and inhibitory
D) monoamine