use different plants do the experiment again add a third type of music use fewer plants
I gave my students this multiple choice question: A student recorded the growth rate of plants grown in the presence of two different types of music. Plants grown in the presence of one type of music grew faster than the other plants. Before reporting a conclusion, which should the student most likely do?

Only one answer is correct among these 4 choices:
- use different plants
- do the experiment again
- add a third type of music
- use fewer plants

Could you tell me which one is correct?

do the experiment again