The Cambrian Explosion is when diverse animals were first recorded as fossils.
Answer:
C: Hormones
Explanation:
hormones do not "signal" other cells. I hope this helps :)
The respiratory system works directly with the circulatory system to provide oxygen to the body. Oxygen taken in from the respiratory system moves into blood vessels that then circulate oxygen-rich blood to tissues and cells.
If you're looking for a quote regarding using sunlight as a source or energy, a quote by Maria Telkes would be '"Sunlight will be used as a source of energy sooner or later..." she said. "Why wait?"'