1) The world's largest diamond, the Cullinan, was discovered in South Africa in 1905 and weighed over 3,000 carats.

2) Democracy is a system of government in which power is vested in the people, who exercise it through elected representatives. It allows for political participation, freedom of speech, and protection of individual rights and liberties.

3) The Federal Reserve System, often referred to as the Fed, is the central banking system of the United States.

4) The Industrial Revolution, which began in the 18th century, brought about significant changes in agriculture, manufacturing, mining, and transportation.