Why is it important for your heart to keep oxygen-rich blood separate from oxygen-poor blood?

An atom of nitrogen had seven protons in its nucleus. how many electrons does it have

An example of a trait that would be considered acquired and inherited is a. a cleft chin b. muscle tone c. scar tissue d. freckled skin

Identify characteristics of energy from the sun. check all that apply. almost all of the energy on earth comes from the sun. energy from the sun is known as mechanical energy. the energy in fossil fuels originally came from the sun. plants convert the energy of sunlight into chemical energy.