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

2) The word "school" contains two vowels: O and O.

3) The concept of political stability refers to the ability of a government or political system to maintain continuity, order, and effective governance over a prolonged period, promoting social cohesion and economic development.

4) The word "piano" contains three vowels: I, A, and O.