Final answer:
Rats with clean air instead of cigarettes air are called control rats or non-smoke-exposed rats in biology.
Step-by-step explanation:
Rats exposed to clean air instead of cigarette smoke are often used in studies to understand the effects of smoking on health. These rats are called control rats or non-smoke-exposed rats. By comparing the control rats to rats exposed to cigarette smoke, scientists can investigate the specific health effects attributed to smoking.