He was paying attention to the teacher's talk during the class.

He thinks that war is a necessary evil.

This issue requires attention.

The air in this area is greatly affected by pollutants emitted from factories.

The existence of dark matter has not yet been fully proven.

Antibiotics don't work for colds, so please don't take them unnecessarily.

It is said that antimatter has properties opposite to those of matter.

We exist as a part of the material world.

This food may contain carcinogens.

Electromagnetic radiation conveys energy in forms such as light and radio waves.