H ( hydrogen ) is the answer I believe.
There are 12 Hydrogens (H) and 12 Oxygens (O) and 6 molecules of Hydrogen Peroxide (H2O2) reacted
I would say it is a chemical change because after a while, the nails start to rust. Now they only rust after about a week though. But rust is a chemical change.
The answer is B. 6CO2+H2O yields C6H12O6+ 6H20.
D. radioactive isotopes are one of the environmental waste products of nuclear energy.
