What Experiment Did Loewi Perform to Show That Most Synapses

What experiment did Loewi perform to show that most synapses are chemical?

A) He dissected the brains of patients who had suffered strokes.
B) He altered the heart rate in frogs by bathing one heart in the chemical solution he collected from another heart.
C) He applied electricity to frogs' legs to animate them.
D) He measured the speed at which neurons sent electrical signals and compared that to the speed of electrical current in a wire.