1) The ancient city of Athens, Greece, is often considered the birthplace of democracy, where citizens had a say in the decision-making process.

2) The word "mountain" contains three vowels: O, U, and A.

3) The process of nuclear fusion powers the sun and other stars, fusing hydrogen atoms together to form helium and releasing vast amounts of energy in the process.

4) The process of photosynthesis, performed by plants, algae, and some bacteria, is responsible for producing the oxygen we breathe.