According to both indigenous American and European accounts and documents, American civilizations at the time of European encounter had achieved many accomplishments. For instance, the Aztecs built one of the largest cities in the world, Tenochtitlan, the ancient site of Mexico City, with an estimated population of 200,000. American civilizations also displayed impressive accomplishments in astronomy and mathematics. The domestication of maize or corn required thousands of years of selective breeding.
What had the Aztec civilization constructed?
one of the largest cities in the world

These troubles were followed in 1347 by the Black Death, a pandemic that spread throughout Europe during the following three years.[AC] The death toll was probably about 35 million people in Europe, about one-third of the population. Towns were especially hard-hit because of their crowded conditions.[AD] Large areas of land were left sparsely inhabited, and in some places fields were left unworked. Wages rose as landlords sought to entice the reduced number of available workers to their fields. Further problems were lower rents and lower demand for food, both of which cut into agricultural income. Urban workers also felt that they had a right to greater earnings, and popular uprisings broke out across Europe. Among the uprisings were the jacquerie in France, the Peasants' Revolt in England, and revolts in the cities of Florence in Italy and Ghent and Bruges in Flanders. The trauma of the plague led to an increased piety throughout Europe, manifested by the foundation of new charities, the self-mortification of the flagellants, and the scapegoating of Jews. Conditions were further unsettled by the return of the plague throughout the rest of the 14th century; it continued to strike Europe periodically during the rest of the Middle Ages.
How many million people died from the Black Death?
35

An antenna (plural antennae or antennas), or aerial, is an electrical device which converts electric power into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter supplies an electric current oscillating at radio frequency (i.e. a high frequency alternating current (AC)) to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is applied to a receiver to be amplified.
What process associated with antennas produces a high frequency alternating current?
transmission