to ensure that the cabbages are safe for human consumption to discover the scientific principle that causes the increased growth to confirm that the observed differences were caused by the fertilizer to determine the difference between the experimental and control groups
I gave my students this multiple choice question: Scientists determined that cabbages grown using Fertilizer A grew bigger than cabbages grown using Fertilizer B or no fertilizer at all. The scientists repeated the investigation and produced the same results. Which best explains the purpose of repeating this investigation?

Only one answer is correct among these 4 choices:
- to ensure that the cabbages are safe for human consumption
- to discover the scientific principle that causes the increased growth
- to confirm that the observed differences were caused by the fertilizer
- to determine the difference between the experimental and control groups

Could you tell me which one is correct?

to confirm that the observed differences were caused by the fertilizer