Which of the following is true of veins? They always carry oxygenated blood.
They always carry deoxygenated blood.
They are the site of exchange of gases, nurtients, and wastes between the blood
and the surrounding tissues.
They always carry blood away from the heart.
They always carry blood toward the heart.

answer: wheres the options

explanation:

the atomic number of magnesium is 12. its nucleus must contain 12 protons and no electrons. the atomic number of an atom is determined by the number of protons.

magnesium is an electrolyte injection commonly used to treat low magnesium levels in your blood. it is also used to prevent or control seizures in women with preeclampsia or eclampsia.