I believe the term for an observable trait of an organism would be called or noted as the organism's phenotype.
No, cladograms deal with living species.
To get an average, you must add all of the numbers together, and divide that sum by the amount of numbers there are. There are 6 number, which is what we must divide by.
6.8g is the average for the set of measurements.
Basically you can answer the question if you know the meaning of 32P and of 35S.
32P means Phosporus-32 (32 is the mass) and 35S means the Sulfur isotope with mass of 35 (it's the most radioactive of all the sulfur isotopes btw).
So we can see that the names have to do with Sulfur and Phosphorus - therefore, the best answer is the following one:
<span>C. Because DNA contains phosphorus and proteins contain sulfur</span>
