the depth of the soil the temperature of the water the number of days until the seeds sprout the size of pot used for growing the seeds
I gave my students this multiple choice question: Marta and Roger are comparing how long it takes two different types of seeds to sprout. They plant both types of seeds in similar pots, place them in a sunny window, and water them daily. If they want to conduct their investigation correctly, which information is most important to record?

Only one answer is correct among these 4 choices:
- the depth of the soil
- the temperature of the water
- the number of days until the seeds sprout
- the size of pot used for growing the seeds

Could you tell me which one is correct?

the number of days until the seeds sprout