Nuclear reactions are used for mass production of energy.

Thermonuclear reactions are the source of the sun's energy.

When the sun rises, a new day begins.

We should use more renewable energy.

This chemical reaction is very dangerous.

This chemical reacts when heat is added.

We are using LED bulbs for energy saving.

In physics, the study of the 'nucleus' at the center of an atom is important.

The source of this river is halfway up the mountain.

He missed school because he had a fever.