Answer :
Final answer:
Controlled experiments test one variable while keeping others constant, with testing multiple variables posing challenges in isolating individual impacts.
Explanation:
Controlled experiments involve testing one variable while keeping other factors constant. The most difficult part of a controlled experiment is testing multiple variables because doing so makes it challenging to determine the specific impact of each individual variable.
Learn more about Controlled experiments here:
https://brainly.com/question/11278941
