When Otto Loewi Collected the Fluid from Synapses That Were

When Otto Loewi collected the fluid from synapses that were involved in slowing a frog's heart, then injected it near the heart of a second frog, he demonstrated that

A) neurotransmitters which are inhibitory can also be excitatory.
B) at least some neurons communicate by releasing chemicals.
C) neurons do NOT communicate by releasing chemicals.
D) communication between a neuron and a muscle is very different than that between two neurons.