Count the number of whiteflies on the peppers before and after planting marigolds. Count the number of whiteflies on the marigolds near the peppers. Kill the whiteflies on other plants in the garden except on the peppers. Put whiteflies on other garden plants and see what happens.
I gave my students this multiple choice question: In your garden, you want to plant marigolds all around your pepper plants because you read that this flower repels whiteflies. How can you test to see if marigolds really do repel whiteflies?

Only one answer is correct among these 4 choices:
- Count the number of whiteflies on the peppers before and after planting marigolds.
- Count the number of whiteflies on the marigolds near the peppers.
- Kill the whiteflies on other plants in the garden except on the peppers.
- Put whiteflies on other garden plants and see what happens.

Could you tell me which one is correct?

Count the number of whiteflies on the peppers before and after planting marigolds.