size of seeds and amount of solution used time of day and number of seeds germinated type of detergent and amount of solution used number of seeds germinated and average length of shoot
I gave my students this multiple choice question: A student conducts an experiment to determine the effect soap has on the growth of radish seeds. He puts 30 seeds in three different dishes: one with water, one with a 1% soap solution, and one with a 10% soap solution. Which type of data should he collect?

Only one answer is correct among these 4 choices:
- size of seeds and amount of solution used
- time of day and number of seeds germinated
- type of detergent and amount of solution used
- number of seeds germinated and average length of shoot

Could you tell me which one is correct?

time of day and number of seeds germinated