The correct answer is C. At same conditions, water is the substance with the highest density. Density of water at STP is 1000 kg/m^3, hydrogen is 0.09 kg/m^3 and oxygen is 1.43 kg/m^3. From the values, it is clear water has the highest density.
Water ( at the same conditions)
Water is the answer. It is a liquid at room temperature whereas hydrogen and oxygen are gases.
The correct answer is Water
Water is the most dense compound of all the mentioned ones. Hydrogen and Oxygen are gasses.