Priscilla Catenaro, age 13, of Bridgeport, Conn., for her question:

HOW MUCH BLOOD DOES A PERSON HAVE?

The amount of blood in your body depends on your size and your environment.

The nine pound baby will only have about 10 ounces of blood. But by the time the child weighs about 80 pounds, a few years later, the amount of blood will have increased to about two and a half quarts.

An adult who weighs about 160 pounds will have about five quarts of blood moving through his veins and arteries.

People who live in high altitudes, where there is less oxygenin the air, could have up to two more quarts of blood than those who live near sea level. The extra blood helps capture the oxygen that is needed by the body.