The Little Ice Age was significant because A) it caused the warming of the earth by 2-3°C.
B) of huge fluctuations in temperatures and the powerful storms that came with those
temperatures
C) people were burning more coal fires and contributing to air pollution
D people were starving as a result of colder temperatures not allowing for long enough growing
seasons to provide an ample food supply

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:

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.