Answer: It's not blocked
https://www.khanacademy.org/science/high-school-biology/hs-human-body-systems/hs-body-structure-and-homeostasis/a/tissues-organs-organ-systems
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.
The sun is considered a giant star so C)
Option B is the correct answer
