Final answer:
Without the detailed chart, we cannot determine which substance is in a gas state. Gases are identified by having no definite shape or volume, ability to compress, and very low densities. Specific data from the chart about each substance's properties would be needed to make an accurate conclusion.
Step-by-step explanation:
To determine which substance is in a gas form from the chart provided, we would need to look for properties that are characteristic of gases. Gases have no definite shape or volume, and they expand to fill their container. They are also able to compress and have extremely low densities compared to liquids and solids. So, the substance that exhibits these properties would be the one in a gas state at room temperature.
Identifying Gases
Unfortunately, the detailed chart with the specific properties of substances A, B, C, and the unknown substance was not provided here. Generally, you can look for clues like low boiling points indicating the substance is a gas at room temperature. With the mentioned substances like oxygen, carbon dioxide, and mercury in different states at room temperature, it is clear oxygen and carbon dioxide are gases, while mercury is a liquid and most metals are solids.
To answer the question accurately, we would need additional data from the chart mentioned in your question.