An experimenter wanted to test the effects of cigarette smoking on rats. she infused the cages of 50 rats with cigarette smoke and the cages of another 50 rats with pure, clean air. the rats that received the clean air were the

Control group

Explanation:

A control group is a group of individuals in an experiment where the independent variable being tested (the exposition to cigarette smoke in this case) can't influence the results. This control group will be then compared to the experimental group (exposed to the smoke) to see the effect of the variable evaluated.

I hope you find this information usefula nd interesting! Good luck!

i'd say that the moon rock is about 2.2 billion years old.

spiders belong to a group of arachnids.

arachnids have the following traits :

they have two body parts.

they have eight legs unlike insects which have 6 legs.

they have no wings.

these traits distinguish them from insects.

the information that antonio is doubting us the statement that spiders differences are as a result of being first to evolve.

this is because the evolution of one species is independent of the other species.