With parallel flow, diffusion of urea happened at regions I and II but not at regions III, IV, or V because... A
Urea was too big to fit through the pores in regions III, IV, or V.
B
There was no concentration gradient for urea in regions III, IV, or V.
С
There was no urea in the blood in regions III, IV, and V.
D
The pore size was too small in regions III, IV, and V.

Which of the following statements is true? 1. the mantle of the earth is made of solid nickel and iron. 2. the crust of the earth is made of solid nickel and iron. 3. the inner core is made of solid nickel and iron.

Humans are believed to have evolved in coastal regions in east africa. the region had an abundant supply of fish for early humanoids to eat. when scientists analyze the fads gene they see an interesting pattern. people whose families have lived in this area of east africa for generation show a high level of diversity in alleles for the fads gene. conversely, people whose families had migrated inland a moderate distance from sources of fish showed a much lower diversity for fads gene alleles. additionally, the fads alleles found in people whose family has lived inland for generation are almost all gene alleles which produce fads proteins with a high level of function and activity. how do anthropologists explain this?

What happens during the experiment stage of the scientific method