What are 3 chemicals used in digestion and what do they do?

The phlogiston theory in the 17th century attempted to explain burning. the theory stated that combustable objects contained a material called phlogiston, a substance without mass, color, odor, etc. after objects burned, the objects were dephlogistonated and were then in their true form. the phlogiston theory was accepted until the 18th century, when lavoisier proved that combustion requires a gas that has mass. phlogiston is considered a) to be scientific knowledge b) not to be scientific knowledge c) to be proven by scientific method d) to be accepted in the modern scientific community

Why are scientists concerned about the depletion of the ozone levels in the stratosphere?

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?