Answer:
A. It's a reliable source because it's from the government, not a website based on other people's opinions.
The same copies of the dna with the genes is distributed in all the cells of the body. This makes all the cells of the body to have the same genetic material. In lower organisms, dna replication is necessary for reproduction in order to have the same genes in the progeny.
Circulatory system pumps blood from the heart to the lungs to get oxygen. The heart then sends oxygenated blood through arteries to the rest of the body. The veins carry oxygen-poor blood back to the heart to start the circulation process over. Your circulatory system is critical to healthy organs, muscles and tissues.
It's the Immune system!
good luck
