(comprehension) Fill in the blank with the letter of the correct choice. A. INCREASE B. DECREASE C. STAY THE SAME 16. When a When a person smokes cigarettes, the action of the cilia in the respiratory tract will – As your leg muscles contract, the amount of blood returning to your right atrium will As the blood travels through the inferior vena cava into the right atrium, the amount of CO2 18. present in the blood will 19. the rate of As blood travels from the aorta, through arterioles, and then into the capillaries of the kidney, the rate of blood flow will gh arterioles, and then into the caillaries of the kidney, ©2016 Education Resources Human Biology: Condensed