two hydrogen bonds are formed between adenine and thymine
<u>Answer</u>: C) Directional selection occurs when one of two extreme phenotypes is selected for.
The type of natural selection known as directional selection is defined in population genetics in the case in which an extreme phenotype is favored over other phenotype. Thus, the population and its allele frequency will evolve towards this end of the trait spectrum (extreme phenotype). This is also the case illustrated in the graph where the right side represents the extreme phenotype.
<span>The production of red blood cells, which transport oxygen, is triggered by a low level of oxygen in the blood. is correct.</span>
