In order for a new species to develop, there must be a change in the А) migration patterns of a population
B) genetic makeup of an existing species.
С) rate of succession in the environment.
D) temperature of the environment.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

i am positive it is c. condensing but i may be wrong

a and c are the answeres