Answer:
A. A pairs with U
Explanation:
In DNA, the nitrogenous bases are A, T, G, and C. In RNA, the nitrogenous bases are A, U, G, and C.
A pairs with U in RNA because it requires less energy to use uracil over thymine.
Hope that helps.
Yes, It seems that evolution has occurred in this area.
Explanation:
Evolution refers to a phenomena in which new traits or alleles that favor a better survival of organisms in a given environment, become fixed in the population.
Evolution is characterized by appearance of new characters and change in allele frequencies.
In the given situation we find that the frequency of the recessive allele in the population has changed over time and the percentage has become fixed.
So, we can say that evolution has occurred in the robin population
