Final answer:
Air, mercury, and water are fluids at room temperature and atmospheric pressure, while glass is a solid. Mercury is unique for being a liquid metal in these conditions.
Step-by-step explanation:
Among the substances listed - air, mercury, water, and glass - the fluids at room temperature and atmospheric pressure are air, mercury, and water. Glass, on the other hand, is an amorphous solid at room temperature and does not flow under normal conditions.
Mercury is an anomaly among metals as it exists as a liquid at room temperature. Water is also a liquid at these conditions, characterized by having a definite volume but no definite shape. Meanwhile, air is a gas, which also qualifies as a fluid due to its ability to flow and take the shape of its container.