In some experiments, several identical groups are set up, keeping conditions similar among them. in the group, a change is deliberately introduced. in the group, this change is not introduced. in this way, the researcher can determine if the change has an effect.

In some experiments, several identical groups are set up, keeping conditions similar among them. In the experimental group, a change is deliberately introduced. In the control group, this change is not introduced. In this way, the researcher can determine if the change has an effect.

Explanation:

In every experiment that has to do with having a replicate, there must be a control group which is used to checkmate the effect of what is being tested, hence; nothing is introduced in the control group unlike the experimental group

the answer would be 3