Using alcohols as solvents offers the advantage of using ro- ions which are somewhat stronger than the hydroxide ion.

The answer is "Ro-ions which are somewhat stronger bases than the hydroxide ion.
These ro-ions are also known as alkoxide ions, and these are stronger bases. the reason behind this is that the alcohols are weaker acids than the water. Alcohols are also used as solvent in some organic reactions and this offers and advantage to use ro-ions.

C. which metal is less dense