Explanation:

Gases at Room Temperature:
At room temperature, oxygen (O2), nitrogen (N2), and hydrogen (H2) exist in the gaseous state. This means that they are in the form of gas and not in the form of solids or liquids. The particles of these gases have a high kinetic energy and are able to move freely, filling the space available to them. They do not have a definite shape or volume.

Gaseous State:
The gaseous state is one of the three common states of matter, along with the solid and liquid states. Gases are characterized by their ability to expand to fill any container, their low density compared to solids and liquids, and their fast and random particle movement. They have weak intermolecular forces and are highly compressible.

Oxygen (O2):
Oxygen is a colorless and odorless gas that makes up approximately 21% of the Earth's atmosphere. It is essential for the survival of most organisms, as it is involved in cellular respiration, combustion, and various other processes. Oxygen is also used in various industries, such as medicine, welding, and rocket propulsion.

Nitrogen (N2):
Nitrogen is a colorless and odorless gas that makes up approximately 78% of the Earth's atmosphere. It is an essential element for life and is found in proteins, nucleic acids, and other biological molecules. Nitrogen is also used in various industrial processes, such as the production of ammonia, fertilizers, and explosives.

Hydrogen (H2):
Hydrogen is the lightest and most abundant element in the universe. It is a colorless and odorless gas that is highly flammable. Hydrogen is used in a wide range of applications, including the production of ammonia, methanol, and various other chemicals. It is also used as a fuel in fuel cells and as a rocket propellant.

Conclusion:
In conclusion, oxygen, nitrogen, and hydrogen are all grouped together because at room temperature, they exist in the gaseous state. They are not suspended particles, colloids, or solids. Understanding the state of matter of different substances is important in various scientific and everyday contexts.