Question

Katie wants to do an experiment to test what factors affect the growth rate of sunflowers. She plants two groups of sunflower seeds in identical pots, gives them the same amount of fertilizer, and lets them sit in the sun for the same amount of time every day. She gives one group of seeds 10 mL of water a day. She gives the other group 1 mL of water a day. The group that receives 10 mL of water grows the fastest. Katie analyzes and publishes her results.

Based on the results of Katie's experiment, what question could she ask next to continue her research on sunflower growth rate?
A.
Will the growth rate of the sunflowers change if Katie increases the amount of water given to 20 mL a day?
B.
Will sunflowers grow to a larger maximum size in rocky mountain soil or in sandy soil from the beach?
C.
Will the growth rate of other flowers, such as roses, be affected by the amount of fertilizer given per day?
D.
Will sunflower petals be a brighter yellow if Katie adds yellow dye into the water that she gives them every day?
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Answer 1

A.

This directly follows Katie's result by testing whether more water (the same variable she changed) continues to increase growth rate. It keeps other conditions the same so she can isolate the effect of water amount.