1) When most people think of big cities, picture London, Hong Kong, or New York. 2) Actually, the world's largest city is Mexico City, and which has about 20 million inhabitants. 3) The modern city was founded by the Spaniards in 1521 on the ruins of the ancient Aztec capital. 4) They destroyed and built the new city in sixteenth-century European style, and with a large public plaza as the city's centre. 5) By stretching from this plaza like the spokes of a wheel are several wide avenues that lead into the city. 6) Before Mexico's independence in 1821 served as the capital of the Spanish Empire in America. 7) In 1847, during Mexico's war with the United States, the city was invaded by American troops. 8) Today, Mexico City is the capital of the largest nation in Central America, and which may one day become an economic powerhouse in the Western Hemisphere.

1) When scholars of rhetoric discuss public oratory, first think of Marcus Tullius Cicero (106 BC–43 BC). 2) Cicero was the greatest Roman orator, and who was also a disciple of stoicism. 3) Stoicism is a philosophy where it is believed that only by doing one's duty can one achieve true freedom. 4) Cicero was also a great statesman who was devoted to the republican form of government. 5) Indeed, even though Cicero was a member of the aristocracy does not mean that he did not love the republic and oppose the rise of would-be dictators like Julius Caesar.

1) Fingerprinting is very old. 2) As a matter of fact, as a method for identifying people has been used for centuries. 3) However, modern fingerprinting techniques were developed only in the nineteenth century, and by an Englishman named Sir Francis Galton. 4) Galton's methods made fingerprinting far more reliable than it had ever been. 5) At first, fingerprints were used only to identify and prove charges against criminals. 6) Today, some countries fingerprint members of the military as well as who work in sensitive government positions and visitors from other countries. 7) In the U.S., the FBI collects, stores, and maintains the world's largest bank of fingerprint files in Washington, DC.

1) Ishmael is a Biblical figure, and who was the son of the patriarch Abraham. 2) However, just because he was Abraham's son didn't make him the son of Abraham's wife, Sarah. 3) As a matter of fact, Ishmael's mother was Hagar, who served Sarah as a handmaid. 4) By being the mother of Isaac, another of Abraham's sons, Sarah demanded that Hagar and Ishmael be exiled. 5) On the other hand, Hagar and Ishmael were sent from their home into the desert. 6) Since that day, the name Ishmael has come to mean "outcast." 7) Interestingly, when Herman Melville sat down to write his famous novel Moby Dick, began with the line: "Call me Ishmael."

1) Oxidation is when electrons in an atom are lost during a chemical reaction. 2) This happens when the electrons combine with oxygen, and which is one of the most abundant elements on earth. 3) A complementary process is reduction, and which is where a substance gives up oxygen. 4) When losing oxygen adds electrons in an atom.