I think the correct answer from the choices listed above is the third option. The barrel of a gun is also known as bore. The barrel is the metal tube which the bullet is fired and the bore is the inside of the barrel. It is the one closest to the barrel so it must be the answer.
Hydrogen isn’t one of the primary macronutrients
Answer:
The respiratory system works directly with the circulatory system to provide oxygen to the body. Oxygen taken in from the respiratory system moves into blood vessels that then circulate oxygen-rich blood to tissues and cells.
