Answer:
Explanation: When a substance is in the gas phase, the quality that will stay constant is:O. The position of particles.In the gas phase, particles are in constant motion and move freely, filling the container they occupy. However, the position of individual particles is not fixed; they move randomly and independently of one another. Therefore, the position of particles is not constant, but rather changes as they move throughout the container.The other options are not constant in the gas phase:Mass: Gas particles can have different masses, and the total mass of the gas can change if particles are added or removed.Shape: Gas particles do not have a fixed shape; they take the shape of their container. Therefore, the shape of the gas can change depending on the shape of the container.Volume: Gas particles can expand or compress to fill the volume of their container, so the volume of the gas is not constant.