What are the basic shapes into which astronomers classify most galaxies?

Astronomers usually classify galaxies in three basic shapes which are spiral, elliptical, and irregular

Galaxy is a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction. Galaxies exist in many different sizes, shapes and brightness. They may exist alone or in larger groups called clusters. Galaxies are divided into three basic types: spirals, elliptical and irregulars. The Milky Way is a spiral galaxy where we live.

significant amounts of nitrogen oxides, carbon monoxide, and other pollution

explanation:

passenger vehicles are a major pollution contributor, producing significant amounts of nitrogen oxides, carbon monoxide, and other pollution. in 2013, transportation contributed more than half of the carbon monoxide and nitrogen oxides, and almost a quarter of the hydrocarbons emitted into our air.

rising temperatures because when water vapor in the air is cooled, it condenses. it turns back into a liquid and attaches to dust particles in the air. these very small water droplets group together to form clouds