In chemistry class, I learned about basic oxides.

Amphoteric oxides have the characteristic of reacting with both acids and bases.

In chemistry class, I learned about the reactions of acid anhydrides.

Acidic oxides react with water to produce acids.

Aluminum is an amphoteric oxide, it reacts with both acids and bases.

Basic oxides react with acids to produce salt and water.

Essential amino acids cannot be produced in the body, so they need to be obtained from the diet.

My father is thirty-nine years old.

This factory has significantly reduced its carbon dioxide emissions.

São Tomé and Príncipe is an island country in Africa.