If two fluids do not mix but rather form two layers

When is your breathing likely to speed up? a. when your white blood cells increase b. when your cells need more energy c. when your heart cells need more carbon dioxide d. when your blood cells have too much oxygen

Which characteristics must an object possess in order to be considered alive?

Why do the circulatory systems of land vertebrates have separate circuits to the lungs and to the rest of the body?