It can be all of them beneficial neutral & organism
I think it's D, because theoretical yield is like, the yield you'd get if 100% of the reactants formed to make product. Well that's how I think of it, but it has something to do with limiting reagents and stuff. Sorry this isn't a really detailed explanation.
Answer:
Temperature gradient = 30
90F - 60F = 30F
The temperature gradient is 30F.
If I am right, let me know.