Which two tubes validated the results?

• A. tubes 1 and 2
• B. tubes 3 and 4
• C. tubes 2 and 5
• D. tubes 4 and 5

Answer: (B)

Validation in this kind of experiment relies on control conditions that prove the assay is working as intended. The two tubes that were chosen provide the expected baseline and a known, consistent response under standard conditions, so they confirm that the measurements you see in the other tubes reflect real, manipulated effects rather than instrument error, reagent failure, or timing issues. When these controls behave as expected, you can trust that any differences observed among the other tubes are due to the experimental variables being tested, not to random problems. The other combinations wouldn’t offer this level of confirmation because they either lack a proper baseline or don’t produce the anticipated, interpretable response, making it hard to distinguish true effects from artifacts.