According to anthropologists, people in preindustrial societies spent 3 to 4 hours per day or about 20 hours per week doing the work necessary for life. Modern comparisons of the amount of work performed per week, however, begin with the Industrial Revolution (1760-1840) when 10- to 12-hour workdays with six workdays per week were the norm. Even with extensive time devoted to work, however, both incomes and standards of living were low. As incomes rose near the end of the Industrial Revolution, it became increasingly common to treat Saturday afternoons as a half-day holiday. The half holiday had become standard practice in Britain by the 1870's, but did not become common in the United States until the 1920's.
In the United States, the first third of the twentieth century saw the workweek move from 60 hours per week to just under 50 hours by the start of the 1930's. In 1914 Henry Ford reduced daily work hours at his automobile plants from 9 to 8. In 1926 he announced that henceforth his factories would close for the entire day on Saturday. At the time, Ford received criticism from other firms such as United States Steel and Westinghouse, but the idea was popular with workers.
The Depression years of the 1930's brought with them the notion of job sharing to spread available work around; the workweek dropped to a modem low for the United States of 35 hours. In 1938 the Fair Labor Standards Act mandated a weekly maximum of 40 hours to begin in 1940,and since that time the 8-hour day, 5-day workweek has been the standard in the United States.
Adjustments in various places, however, show that this standard is not immutable. In 1987, for example, German metalworkers struck for and received a 37.5-hour workweek; and in 1990 many workers in Britain won a 37-hour week. Since 1989, the Japanese government has moved from a 6- to a 5-day workweek and has set a national target of 1,800 work hours per year for the average worker. The average amount of work per year in Japan in 1989 was 2,088 hours per worker,compared to 1,957 for the United States and 1,646 for France.

In July of 1994, an astounding series of events took place. The world anxiously watched as,every few hours, a hurtling chunk of comet plunged into the atmosphere of Jupiter. All of the twenty-odd fragments, collectively called comet Shoemaker-Levy 9 after its discoverers, were once part of the same object, now dismembered and strung out along the same orbit. This cometary train, glistening like a string of pearls, had been first glimpsed only a few months before its fateful impact with Jupiter, and rather quickly scientists had predicted that the fragments were on a collision course with the giant planet. The impact caused an explosion clearly visible from Earth, a bright flaming fire that quickly expanded as each icy mass incinerated itself. When each fragment slammed at 60 kilometers per second into the dense atmosphere, its immense kinetic energy was transformed into heat, producing a superheated fireball that was ejected back through the tunnel the fragment had made a few seconds earlier. The residues from these explosions left huge black marks on the face of Jupiter, some of which have stretched out to form dark ribbons.
Although this impact event was of considerable scientific import, it especially piqued public curiosity and interest. Photographs of each collision made the evening television newscast and were posted on the Internet. This was possibly the most open scientific endeavor in history. The face of the largest planet in the solar system was changed before our very eyes. And for the very first time, most of humanity came to fully appreciate the fact that we ourselves live on a similar target, a world subject to catastrophe by random assaults from celestial bodies. That realization was a surprise to many, but it should not have been. One of the great truths revealed by the last few decades of planetary exploration is that collisions between bodies of all sizes are relatively commonplace, at least in geologic terms, and were even more frequent in the early solar system.

托福阅读题目：
1. What does the passage mainly discuss?
(A) Why people in preindustrial societies worked few hours per week
(B) Changes that have occurred in the number of hours that people work per week
(C)A comparison of the number of hours worked per year in several industries
(D) Working conditions during the Industrial Revolution
2. Compared to preiudustrial times, the number of hours in the workweek in the nineteenth
century
(A) remained constant
(B) decreased slightly
(C) decreased significantly
(D) increased significantly
3. The word "norm" in line 5 is closest in meaning to
(A) minimum.
(B) example
(C) possibility
(D) standard
4. The word "henceforth" in line 13 is closest in meaning to
(A) in the end
(B) for a brief period
(C) from that time on
(D) on occasion
5. The "idea" mentioned in line 15 refers to
(A) the 60-hour workweek
(B) the reduction in the cost of automobiles
(C) the reduction in the workweek at some automobile factories
(D) the criticism of Ford by United States Steel and Westinghouse