[简答题]Not until the twentieth century did engineers fully understand the principles of flight that birds have been using for millions of years.

[单项选择]

Until the twentieth century cigarettes were not an important threat to public health. Men used tobacco mainly in the form of cigars, chewing tobacco, pipe tobacco, and snuff(鼻烟). Most women did not use tobacco at all.
The cigarettes industry began in the 1870s with the development of the cigarette manufacturing machine. This made it possible to produce great numbers of cigarettes very quickly, and it reduced the price.
Today cigarette smoking is a widespread habit. About forty-three percent of adult men and thirty-one percent of adult women in the United States smoke cigarettes regularly. It is encouraging to note, however, that millions of people have given up the smoking habit. Seventy-five percent of the male population and forty-six percent of the female population have smoked cigarettes at some time during their lives, but twenty-six percent of these men and eleven percent of women have stopped smoking. The number of persons who have given up smoking is incre
A. snuff
B. cigarettes
C. pipe tobacco
D. cigars

[单项选择]

Until the 20th century cigarette smoking was not a widespread habit. The cigarette industry started in the 1870s with the development of cigarette manufacturing machines. It helped produce great numbers of cigarettes very quickly and reduce the price greatly. And consequently more and more people, both men and women, began to smoke cigarettes. Men as a group, however, smoke more than women. But the highest proportion of smokers is found in the age group of 24-44, regardless of sex difference.
Income, education and occupation all play a part in determining a person’s smoking habits. City people smoke more than people living on farms. Well-educated men with high incomes are less likely to smoke cigarettes than men with fewer years of schooling and lower incomes. On the other hand, if a well-educated man with a higher income smokes at all, he is likely to smoke more packs of cigarettes per day.
The situation is somewhat different for women. There are slightly m
A. Before the 1870s.
B. In the year of 1870.
C. When cigarettes were made in large numbers.
D. When women began to smoke cigarettes.

[填空题]Until the middle of 19^th century, all inventions by women ______under the law.

[填空题]Only in the late 18th century did the ______ of grammar rules with translation into target language become popular as the principal practice technique.

[单项选择]What did the 19th century scientists think about our brain [A] Different part of the brain had different effect. [B] Chemical changes stopped during our sleeping; [C] There was a storehouse in the brain.

[单项选择]It wasn’t until the late 19th century that physicians realized that its （　） symptoms were all part of the same disease.
A. perfunctory
B. peremptory
C. perplexing
D. perambulatory

[单项选择]Chemistry did not emerge as a science until after the scientific revolution in the seventeenth century and then only rather slowly and laboriously. But chemical knowledge is as old as history, being almost entirely concerned with the practical arts of living. Cooking is essentially a chemical process, so is the melting of metals and the administration of drugs and potions. This basic chemical knowledge, which was applied in most cases as a rule of thumb, was nevertheless dependent on previous experiment. It also served to stimulate a fundamental curiosity about the processes themselves. New information was always being gained as artisans improved techniques to gain better results.
The development of a scientific approach to chemistry was, however, hampered by several factors. The most serious problem was the vast range of material available and the consequent difficulty of organizing it into some system. In addition, there were social and intellectual difficulties, chemistry is
A. The scientific revolution in the seventeenth century.
B. The reasons why chemistry developed slowly as a science.
C. The practical aspects of chemistry.
D. Difficulties of organizing knowledge systematically.