I would say C is the most correct.
In D it depends on what water source you're using. Let's say it is a waterfall, then the source of the water (melting ice or a lake) may disappear in the future.
If you're using underwater "windmills" placed in the ocean, then you would expect it to last a while as the ocean will not disappear in the near future.
I think chemistry field of science
Atomic Mass Number = Atomic Number + Number of Neutrons
No of moles of fe2o3 = 16.5/(55.8x2+16x3)=0.103mols
No. Of moles of iron= 0.103 x 2 = 0.206mols
Mass of iron = 0.206 x 55.8 = 11.5g