How is the cell membrane selectively permeable? a. The cell membrane allows particles to freely move across the membrane.
b. The cell membrane chooses what will enter and leave the cell.
C. The cell membrane chooses only what will leave the cell.
d. The cell membrane chooses only what will enter the cell.

Explanation:

The cell membrane is selectively permeable, allowing only a limited number of materials to diffuse through its lipid bilayer. ... During passive transport, materials move by simple diffusion or by facilitated diffusion through the membrane, down their concentration gradient.

what's the rest of the question

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.