Answer: Growth rate of the grass seeds.
Step-by-step explanation:
The growth rate is the dependent variable in the experiment because the growth rate of the plants is dependent on the fertilizers. The factor that cannot be changed by the experimenter is known as dependent variable and it is dependent on the independent variables.
The students wants to see the effect of the fertilizers on the growth of the plants. The fertilizer is independent variable which can be changed by the experimenter.
The plants growth depends on many factors, these factors are fertilizers, amount of light, amount of water, et cetera.
Excluding fertilizers rest of the factors are kept same and are controlled factors.