Two models of the same compound are shown. On the left labeled Model A 2 large overlapping black spheres with 3 small blue spheres overlapping the rear black sphere and 2 medium red spheres overlapping the front black sphere. One of the red spheres has a small blue sphere overlapping it. On the right labeled Model B 2 C's connected by a black line. The C on the left has 3 H's attached by 1 black line each and the C on the right has 2 Os attached to it. The top O is attached by 2 black lines and the bottom O by 1 black line. The bottom O also has an H attached to it by 1 black line.
In what way is Model A better than Model B?

Model A shows the types of elements in the compound, but Model B does not.
Model A shows the total number of atoms in the molecule, but Model B does not.
Model A shows the three-dimensional shape of the molecule, but Model B does not.
Model A shows the number of atoms of each element in the molecule, but Model B does not

To answer this question, researchers studied populations of the dusky salamander (desmognathus ochrophaeus) living on different mountain ranges in the southern appalachian mountains. the researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. four mating combinations were tested for each pair of populations (a and b)—two within the same population (female a with male a and female b with male b) and two between populations (female a with male b and female b with male a). the proportion of successful matings for each mating combination was measured. for example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). the reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (aa + bb) minus the sum of the proportion of successful matings of each type between populations (ab + ba). the table provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.