Oxygenated blood in the cardiac system

The correct option is "leaves from left side of the heart".

To understand why this is correct, let us trace the path of blood flow through the human circulatory system step-by-step:
1. Deoxygenated blood from the body's tissues enters the right atrium of the heart and flows into the right ventricle.
2. The right ventricle pumps this deoxygenated blood to the lungs via the pulmonary arteries, where it releases carbon dioxide and absorbs oxygen.
3. Oxygenated blood returns from the lungs to the left atrium of the heart via the pulmonary veins.
4. The oxygenated blood then moves into the left ventricle. From the left ventricle, it is pumped out of the heart through the aorta to distribute oxygen and nutrients to the rest of the body.

Therefore, oxygenated blood leaves the heart from the left side (specifically, the left ventricle) to be distributed throughout the body.