71. The cameras of the Voyager II spacecraft detected six small, previously unseen moons circling Uranus, doubling to 12 the number of satellites now known to orbit the distant planet.

72. Architects and stonemasons, the Maya built huge palace and temple clusters without the benit of animal transport or the wheel.

73. According to a recent poll, owning and living in a freestanding house on its own land is still a goal of a majority of young adults, as it was of earlier generations.

74. Often visible as smog, ozone is formed in the atmosphere when hydrocarbons and nitrogen oxides, two major pollutants emitted by automobiles, react with sunlight.

75. Salt deposits and moisture threaten to destroy the Mohenjo-Daro excavation in Pakistan, the site of an ancient civilization that flourished at the same time as the civilizations in the Nile delta and the river valleys of the Tigris and Euphrates.

76. Never bore had taxpayers confronted as many changes at once as they confronted in the Tax Rorm Act of 1986.

77. Even though the direct costs of malpractice disputes amounted to less than 1 percent of the $541 billion the nation spent on health care last year, doctors say fear of lawsuits plays a major role in health-care inflation.

78. Visitors to the park have often looked up into the leafy canopy and seen monkeys sleeping on the branches, with arms and legs hanging like socks on a clothesline.

79. The Parthenon was a church from 1204 until 1456, when Athens was taken by General Mohammed the Conqueror, the Turkish sultan, who established a mosque in the building and used the Acropolis as a fortress.

80. New hardy varieties of rice show promise of producing high yields without the costly irrigation and application of commercial fertilizer that were required by earlier high-yielding varieties.

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