Cindy Rabbe, age 'l2, of Ottawa, Ontario, Canada, for her question:

WHAT IS SMOKE?

We have smoke when finely divided solid particles become suspended and fixed in a gas. Most smoke is caused by particles of carbon from burning fuel.

More than $1 billion is lost annually in North America as a result of s'moke. In cities automobiles and manufacturing send tons of smoke into the? air causing blackened buildings, corroded metals and damaged vegetables. Human life is also bothered by smoke.

Smoke trapped in a weather condition called an inversion, where there are no vertical air currents to remove the smoke or smog, can be especially dangerous. Much attention these days is being given to the problem of air pollution.