I am busy with work during the daytime.

My keys are inside the house.

This phenomenon occurs cyclically.

This is my first question.

Rare earth elements are essential materials for the manufacture of electronic devices.

An isotope refers to elements with the same atomic number but different numbers of neutrons.

Transition elements play an important role in chemical reactions.

Oxygen, which is one of the chemical elements, is necessary for us to breathe.

If you're hungry, try eating some belly.

My room is the quietest in the house.