[单项选择]It is estimated that ten percent of local children would leave school at 14 to learn a trade．
A. 据说，有10%的当地孩子在14岁左右将要辍学去学习一门手艺。
B. 有10%的人认为，当地孩子在14岁左右就应在离校前学会做生意。
C. 有10%的人估计，当地孩子在14岁左右就会辍学去学一门手艺。
D. 据估计，有10%的当地孩子在14左右就会离开学校去学一门手艺。

[单项选择]It is estimated that ten percent of local children would leave school at 14 to learn a trade．
A. 据说，有10%的当地孩子在14岁左右将要辍学去学习一门手艺。
B. 有10%的人认为，当地孩子在14岁左右就应在离校前学会做生意。
C. 有10%的人估计，当地孩子在14岁左右就会辍学去学一门手艺。
D. 据估计，有10%的当地孩子在14左右就会离开学校去学一门手艺。

[单项选择]It is said that ten percent of the local children would leave school （） about 14 to learn a trade.
A. at
B. of
C. in
D. to

[填空题]The law prevented the （） of children under ten in the cotton mills. (employ)

[单项选择]It has been estimated that only 21 percent of______world’s land surface can be cultivated and that only 7.6 percent is actually under______cultivation.
A. /.../
B. the...the
C. /...the
D. the.../

[单项选择]A study found that 70 percent of children surveyed in 1970 had at one time had cavities, whereas only 50 percent of those surveyed in 1985 had ever had cavities. The researchers concluded that the level of dental disease in children had declined between 1970 and 1985.
Which of the following, if true, would most seriously undermine the researchers’ conclusion presented above
A. Cavities are the most common kind of dental disease to which children are subject.
B. The children surveyed came from a broad variety of income backgrounds.
C. The children surveyed were selected from among students of teachers cooperating with the researchers.
D. The accuracy of cavity detection techniques has improved dramatically since 1970.
E. (E) The children surveyed in 1985 were younger on average than those surveyed in 1970.

[单项选择]About ten percent of the world’s deserts are composed of sand dunes, which are driven across the desert by the wind. Sand grains march across the desert floor under the influence of strong winds by a process known as saltation. The grains of sand become airborne for a moment, and upon landing they dislodge additional sand grains, which repeat the process. In this manner, sand dunes engulf everything in their path, including structures made by people, and pose a major problem in the construction and maintenance of highways and railroads that cross sandy areas of desert. Sand dune migration near desert oases poses another serious problem, especially when encroaching on villages. Methods to mitigate damage to structures from sand dunes include building windbreaks and funneling sand out of the way. Without such measures, disruption of roads, airports, agricultural settlements, and towns could become a major problem in desert regions.
The direction, strength, and variability of the w
A. Their location.
B. Their destructiveness.
C. Their formation.
D. Their disappearanc

[单项选择]（）much of their land is poor and only ten percent of the land can be cultivated, over ninety percent of the population are agricultural workers.
A. Except that
B. Although
C. Because
D. So far as

[单项选择]Industry ______ only ten percent of the smog in Los Angeles.
A. calls on
B. mounts to
C. appeals to
D. accounts for

[填空题]

• A. 10 percent to 25 percent for the proportion of workers who use drugs occasionally on the job
• B. determine exactly when simple drug use becomes abuse
• C. the 1920s until the 1960s
• D. the 1960s until the 1970s
• E. signals passing through the nervous system

Estimates of employee drug use very greatly, ranging from ______.