The answer is b. The second letter (if there is one) is always written as lowercase
<span>The answer is a certain required chemicals must be actively
transported. Blood brain barrier is a
selective membrane that separates blood circulating from the brain and the
fluid of extracellular in the central nervous system. This is also called a
filtering mechanism, the capillaries that carry blood to the brain and spinal
cord tissue blocking the path way of the certain substance.</span>
Oxygen is used by both autotrophs and heterotrophs to release energy from glucose (as we know, the bonds between organic compounds can be used to release energy) in a process known as cellular respiration. Carbon dioxide, however, is predominantly used in autotrophs to perform photosynthesis because they cannot get their food any other way. The type of organism that is both an oxygen producer and carbon dioxide consumer is an autotroph. This is because they release oxygen during photosynthesis and require carbon dioxide to perform photosynthesis.
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