The circulation time of a mammal (the average time it takes for all the blood in the body to circulate once and return to the heart) is proportional to the fourth root of the body mass of the mammal. Circulation time, t, is measured in seconds and body mass, m, is measured in kilograms.

The ancestors of horses possessed feet with five digits. over time, with the development of grasslands, the digits fused and formed hooves. what evolutionary advantage did this transformation serve? a. it allowed them to climb rocky surfaces with ease. b. it allowed them to graze better. c. it enabled them to run faster from predators. d. it let them see clearly through the grasslands. e. it made them taller.