In the SDS-PAGE (sodium dodecylsulfate - polyacrylamide gel electrophoresis) method, separation takes place on the basis of: a. charge only, because all particles have different charges, but the same mass.
b. the sieving action of the gel, because all particles have the same charge, but different masses.
c. the sieving action of the gel, because all particles have approximately the same charge/mass ratio, but different masses.
d. the chemical nature of the buffer used as the electrolyte.

B

Explanation:

Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) is a method of separating molecules based on the difference of their molecular weight.

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 is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.