The answer is D, photosynthesis and respiration.
—Evidence—
Oxygen is a byproduct of photosynthesis and, correspondingly, carbon dioxide the byproduct of respiration.
Oxygen gives our cells the ability to break down food in order to get the energy we need to survive. Although other animals may use different organs to breathe with, they all get oxygen into their bodies through respiration.
Hmm good question. Well I would have to test it for where there are no living life. I would have to build another NASA in the County because there is plenty of room there. Mars is made out of Dusty Crust that is about 30 miles thick. And let's say that the desert's Dusty Crust is about 5 miles - 15 miles thick. That will give about the same amount of surface that mars has. So we would know what to build for a perfect lander to work on Mars. This isn't much but it is something.
Answer:
The wolf population has substantially declined in Canada.
Explanation:
Pls mark brainliest
