Miles Peterson, age 13, of Kalispell, Mont., for his question:

WHAT ARE TRACE ELEMENTS?

Trace elements are minerals needed in small amounts by plants, animals and humans. Major elements such as iron, carbon, sulfur, oxygen, calcium, hydrogen and phosphorus are part of the make up of all living things. The trace elements are also necessary to life.

Scientists know the uses of only a few of these trace elements. However, they do know that these minerals are necessary for the work of certain vital enzymes.

Trace elements include cobalt, magnesium, copper, manganese and zinc.

The body needs copper so it can use iron to build hemoglobin, an important part of red blood cells. Cobalt, contained in vitamin B 12, protects the body against a blood disease called "pernicious anemia."

Magnesium helps to regulate muscle reaction and keeps the muscles in good working condition while plants need magnesium to build chlorophyll.

Manganese and zinc are required for the normal action of certain enzymes. Without these two minerals, certain reactions in the body cells would stop.