Herb Is Watching a Documentary on Dr

Multiple Choice

 Herb is watching a documentary on Dr. Loewi. He learned that neuroscientists first understood that synapses use chemicals to communicate because Dr. Loewi _____.

A) decreased a dog's heart rate and then used adrenaline to speed it up
B) stimulated a frog's heart that was in a fluid bath and then used just the fluid to simulate a second heart
C) measured the reflex speeds in dogs
D) applied adrenaline directly onto a heart muscle