After One Frog's Heart Has Been Stimulated, an Extract of Fluid

Multiple Choice

 After one frog's heart has been stimulated, an extract of fluid from that heart can make a second frog's heart beat faster. What conclusion did Otto Loewi draw from these results?

A) Transmission at synapses is a chemical event.
B) The sympathetic and parasympathetic nervous systems are antagonistic.
C) Transmission at heart muscle synapses is electrical.
D) Hormones facilitate the actions of the nervous system.