using the divergence event labeled 3, an open circle, you would expect 25 amino acid changes/kb between descendent lineages if using gene b as the molecular clock.

i think that the best answer would be c.

tell me if im wrong : )

correct answer is option a.

tropopause, stratopause and mesopause have all in common aspect that is point of maximum temperature in its layer of the atmosphere. all layers of atmosphere observe abrupt change in temperature. tropopause is the boundary between troposphere and stratosphere. stratopause is the boundary between stratosphere and mesosphere. mesopause is the boundary between mesosphere and thermosphere. these all boundaries are ranges between altitude of 0 to 80 km.