Concept:Covalent hydrides may be gases, liquids, or solids at room temperature depending on their intermolecular forces.Explanation:At room temperature, HCl and H2S exist as gases.BH3 is unstable and exists mainly as its dimer B2H6, which is also a gas.H2O remains a liquid at room temperature because strong hydrogen bonding holds its molecules together.Thus, among the given covalent hydrides, H2O is not a gas at room temperature.Answer:A. H2O