I'm having trouble on this too :(
The correct answer is C.) Rainfall
Photosynthesis is the process that plants use to make food, Which requires sun light, minerals from the soil, water, and carbon dioxide. (They turn carbon dioxide to oxygen).
The answer is: the amount of the saliva samples must stay consistent while the amount of starch must vary.
The amount of the saliva samples must stay consistent because amylase, present in the saliva, is the independent variable which affects the dependent variable - the amount of starch. So, amylase will do its job while remaining surface area of the starch will depend on the starting amount of the starch.
She provided important evidence for the presence of JUMPING GENES.
She challenged existing concepts of what genes were capable of when she discovered that some genes could be mobile.