In the year 1910 to 1970, the frequency of allele B has decreased, whereas the frequency of allele b has increased. This event shows a natural selection on a single-gene trait. The increase in the frequency of allele b indicates that nature has favored this trait over the other one. Species with this trait were able to adapt, survive, and reproduce; hence, allele b becomes more common in this population. Therefore, the correct answer is E.

E. The likelihood of surviving and reproducing became higher for individuals with Allele b than for individuals with Allele B.

By comparing the DNA sequences of species, scientists can determine how species are closely related to each other. If two species have a few different mutations in the same gene, this means that they just shared a common ancestor recently. On the other hand, many different mutations would indicate that the species are distantly related.

B. comparing DNA sequences from each species for different genes

In the year 1950, a directional selection took place, wherein nature favored the medium-tan crabs. However, a change in the beach color has occurred over time. This event affected the population of crabs on the beach.

The data in graph B shows a disruptive selection during 1990. This indicates that nature favors the crabs in light tan and dark tan colors, which are on both ends of the graph. This event made the crabs in medium tan color become less common since they appear more visible to the predators; hence, they are more likely to be hunted and consumed.

D. A change in beach color made medium-tan crabs the most visible to predators