One that can be produced as fast as it is used - apex
Nucleic acid
Coal
The ice caps are made of freshwater.
solar power
It forms a salt and water.
Aldehyde
If you have a list of possibilities count the carbon atoms in the formula.
Otherwise there many possibilities, if we restrict ourselves to hydrocarbons:-
hexane, C6H14
hexene C6H12, various isomers
hexyne, C6H10, various isomers
benzene, C6H6.
there are also alcohols, aldehydes ketones carbohydrates metal complexes the list is very large.
polysaccharide
polysaccharide
Hydroelectric
amino
sends electrical impulses to the heart, causing it to beat more regularly
natural gas