Answer:
The correct answer is d.) they have a negative charge
Hydroxide ions, chemical formula OH⁻ are negatively charged anions.
Oxygen is covalently attached with hydrogen in hydroxide ion.
It is important as it can function as base, nucleophile, ligand as well as catalyst.
Chemicals containing hydroxide ions are considered as base. They dissociate in hydroxide ion and their respective cations in aqueous solution.
The Lewis dot structure of hydroxide ion is shown below.