If a cell was observed under the microscope and found to have a rigid cell wall and be green in color that cell is most likely a

Plant cell

Explanation:

Plant cells are rigid. The green color comes from chlorophyll. Plants also have cell walls, because unlike animal cells that have a skeleton to support them, the plant cells need to support themselves.

step 1 ammonium can be absorbed by plants, but some is converted into nitrates which are better for plants to absorb. this is called nitrification. 2. step 2 the deer eats the plants and uses the nitrogen-containing proteins for cell growth. 3. step 3 bacteria in the soil conduct nitrogen fixation to convert nitrogen gas from the atmosphere into ammonium. 4. step 4 some of the nitrates are absorbed back into plants, but denitrification breaks down the nitrates into nitrogen gas released back into the atmosphere. 5. step 5 nitrogen is found in the urine, which gets broken down into ammonium through the process of ammonification. 6. step 6 plants absorb the ammonium and begin assimilation, the process to add the nitrogen to protein.

the answer would be..

b. sucking