It depends on what type of air
earth
Yes earth
It doesn't have air for people to live on that planet
Because it is the only planet that has air
Air is retained on Earth due to Earth's gravity.
All matter, including air has a gravitational pull. The gravity we feel, though is not a product of Earth's atmosphere, which has a tiny mass in proportion to the planet itself. Most of the mass of Earth is rock and metal. That is the source of most of Earth's gravity.
it has air, food and water
Earth is a rock, a non gaseous planet, but earth has an atmosphere comprising of air, a mixture of gases. This does not make it a gas planet. Gas planets have the whole mantle as gas, but earth does not have a gas mantle.
field or atmosphere
They are because they polute the air and water of the earth.
the Air
No, oxygen is a component of the air, at least that's the way it is on planet Earth.