Question

an independent variable is a variable that is changed or manipulated in the experiment. how many independent variables should there be when designing an experiment?

one
as many as you want
two

Explanation:

Identify the core scientific principle

A controlled experiment is designed to test the effect of a single factor on an outcome.

Analyze the role of variables

To establish a clear cause-and-effect relationship, only one factor should be changed at a time.

Determine the correct option

Changing more than one independent variable makes it impossible to determine which variable caused the observed results. Therefore, there should be exactly one independent variable.

Answer:

• one (Correct answer)
• as many as you want
• two