Breathing Helps Move Blood from Lower Parts of the Body

Breathing helps move blood from lower parts of the body toward the heart by which of the following mechanisms?

A) Inhalation increases the size of the thoracic cavity, which reduces pressure and draws blood toward the heart.
B) Inhalation decreases pressure in the abdominal cavity, which opens veins and pushes blood toward the heart.
C) Breathing does not help return blood to the heart.
D) Inhalation increases the size of the thoracic cavity and increases pressure in the abdominal cavity.