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According to United States census data, while there was about one-third of mothers with young children working outside the home in 1975, in 2000, almost two-thirds of those mothers were employed outside the home.
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Clouds are formed from the evaporation of the oceans' water that is warmed by the Sun and rises high into the atmosphere, condensing in tiny droplets on minute particles of dust.
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Schistosomiasis, a disease caused by a parasitic worm, is prevalent in hot, humid climates, and it has become more widespread as irrigation projects have enlarged the habitat of the freshwater snails that are the parasite's hosts for part of its life cycle.
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Sor Juana Inés de la Cruz was making the case for women's equality long before the cause had a name: Born in the mid-seventeenth century in San Miguel Nepantla, Mexico, the convent was the perfect environment for Sor Juana to pursue intellectual pursuits, achieving renown as a mathematician, poet, philosopher, and playwright.
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By devising an instrument made from a rod, wire, and lead balls, and employing uncommonly precise measurements, in 1797–1798 Henry Cavendish's apparatus enabled him to arrive at an astonishingly accurate figure for the weight of the earth.
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The growth projected for these storms in different computerized weather models varies widely.
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By using a process called echolocation to analyze the echoes of the high-pitched sounds they produce, bats can determine not only the distance to an object, but they also can determine its shape and size and the direction in which it is moving.
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Carbon dioxide, which traps heat in the atmosphere and helps regulate the planet's surface temperature, is constantly being exchanged between the atmosphere on the one hand and the oceans and terrestrial plants on the other.
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Floating in the waters of the equatorial Pacific, an array of buoys collects and transmits data on long-term interactions between the ocean and the atmosphere, interactions that affect global climate.
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PREP07 Test 2 OG18-语文分册 OG19-语文分册 OG20-语文分册
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Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America, which, causing plant and animal extinctions, marks the end of the geologic era known as the Cretaceous Period.
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PREP07 Test 2 OG18-语文分册 OG19-语文分册 OG20-语文分册
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Although the first pulsar, or rapidly spinning collapsed star, to be sighted was in the summer of 1967 by graduate student Jocelyn Bell, it had not been announced until February, 1968.
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Sound can travel through water for enormous distances, prevented from dissipating its acoustic energy as a result of boundaries in the ocean created by water layers of different temperatures and densities.
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Last year land values in most parts of the pinelands rose almost so fast, and in some parts even faster than what they did outside the pinelands.
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The North American moose's long legs enable it to move quickly through the woods, stepping easily over downed trees, but predators pursuing it must leap or go around them.
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Early administrative decisions in China's Ming Dynasty eventually caused a drastic fall in tax revenues, a reduction in military preparedness, the collapse of the currency system, and failed to make sufficient investment in vital transportation infrastructure.
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Seismologists studying the earthquake that struck northern California in October 1989 are still investigating some of its mysteries：the unexpected power of the seismic waves,the upward thrust that threw one man straight into the air, and the strange electromagnetic signals detected hours before the temblor.
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The type of behavior exhibited when an animal recognizes itself in a mirror comes within the domain of “theory of mind,” thus is best studied as part of the field of animal cognition.
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Unlike the United States, where farmers can usually depend on rain or snow all year long, the rains in most parts of Sri Lanka are concentrated in the monsoon months, june to September, and the skies are generally clear for the rest of the year.
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In preparation for the prediction of a major earthquake that will hit the state, a satellite-based computer network is being built by the California Office of Emergency Services for identifying earthquake damage and to pinpoint the most affected areas within two hours of the event.
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Once numbering in the millions worldwide, it is estimated that the wolf has declined to 200,000 in 57 countries, some 11,000 of them to be found in the lower 48 United States and Alaska.
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