Answer: Tay-Sachs a disease caused by an absence of an enzyme that break down fatty substance causing damaged to nerve cells
A testable question is B. If a plant is turned upside down, which way will the roots grow?
The other options are incorrect because you cannot create some kind of experiment to prove them right or wrong.
Hope that helped you.
I think this would answer your question. I did this in school and I only got a few wrong....