Otto Loewi Demonstrated That Neurons Communicate by Releasing Chemicals at the Synapse

Otto Loewi demonstrated that neurons communicate by releasing chemicals at the synapse. His research involved

A) collecting fluid from synapses in one frog and transferring them to another frog.
B) injecting purified chemicals at a synapse and using fine electrodes to measure the response of the postsynaptic neuron.
C) radioactively labeling chemicals and tracing where they went.
D) electron microscope analysis.