Read the following paragraph and answer the question. Give ONLY the answer, no other words or explanation.

For example:

Answer: <most likely answer, as short as possible>.

Paragraph: 
Systemic circulation is the longer loop of the cardiovascular system. It carries blood between the heart and the rest of the body. Oxygen-rich blood flows from the heart to cells throughout the body. As it passes cells, the blood releases oxygen and absorbs carbon dioxide. Then the oxygen-poor blood returns to the heart.


Question: In the cardiovascular system, where is the ultimate destination of the oxygen-poor blood?
heart
The heart.