Education about sex is very important.

Understanding the structure of atoms is a fundamental part of physics.

This furnace operates very efficiently.

In this factory, they melt iron using an electric arc furnace.

This area is very safe.

Please use the emergency stairs in case of a fire.

Due to the earthquake, the city declared a state of emergency.

I learned about valence in chemistry class.

The atomic number of helium is 2.

We must not forget the horror of the atomic bomb.