Can someone please help me

The answer is "it controls the rate of breathing by sending hormones through the blood." (A)

For example, this quote states that "The response of the brainstem to increased levels of carbon dioxide in the blood is coordinated with the response of the cardiovascular system. When these chemoreceptors detect such a change, the body responds by regulating blood flow and breathing."

blue stars have the highest surface temp

stellar distances are usually expressed in light-years

the measure of a star's brightness is called magnitude

hope this !

ι вєℓινє тнє αиѕωєя тσ уσυя qυєѕтισи ιѕ в. ℓуѕσѕσмє

ι нσρє тнαт ι ¢συℓ∂ нєℓρ уσυ.