The conclusion is valid because they tested two different brands. The conclusion is invalid because the test had multiple variables. The conclusion is valid because they conducted the investigation in a lab. The conclusion is invalid because the real names of the batteries were hidden.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: In a lab investigation, students use Brand X batteries in a flashlight and Brand Y batteries in a radio. After two hours, the flashlight stops working, but the radio continues to work. As a result, the students conclude that Brand Y batteries last longer. Which statement about the conclusion of the investigation is most accurate?
Possibilities:
- The conclusion is valid because they tested two different brands.
- The conclusion is invalid because the test had multiple variables.
- The conclusion is valid because they conducted the investigation in a lab.
- The conclusion is invalid because the real names of the batteries were hidden.

The conclusion is invalid because the test had multiple variables.