Net primary production = A. Respiration + Photosynthesis B. Photosynthesis - Respiration C. Photosynthesis + Gross primary production D. Gross primary production - respiration

explanation:

the sun shines white and black light to our planet. the white light has all the colors in it. in our upper atmosphere, we have dust particles and oxygen molecules. the white light meaning all of the colors in a rainbow shines through the upper levels of the atmopshere and the blue light scatters across the entire planet. that is why our sky is blue.