问题 选择题

下列何种营养物质,人体对它的需要量很小,但一旦缺乏,却会影响正常的生长和发育,甚至会引起疾病                                           (       )

A.蛋白质

B.糖类

C.维生素

D.无机盐

答案

答案:C

题目分析:蛋白质是细胞修复和组织更新的原料,糖类是主要的供能物质,无机盐具有调节人体代谢等作用。维生素是人和动物为维持正常的生理功能而必需从食物中获得的一类微量有机物质,在人体生长、代谢、发育过程中发挥着重要的作用。维生素既不参与构成人体细胞,也不为人体提供能量。人体对维生素的需要量很小,但是旦缺乏,却会影响正常的生长发育,甚至会引起疾病,故只有选项C符合题意。

单项选择题

The questions in this group are based on the content of a passage. After reading the passage, choose the best answer to each question. Answer all questions following the passage on the basis of what is stated or implied in the passage.

Dear Sirs,

Given all the coverage that the emergence of hybrid cars has received in your pages in recent months, your readers may be interested to learn that gasoline-electric hybrids are not a new phenomenon at all, but rather the latest incarnation of an idea that has been kicking around for over a century. Indeed, the hybrid car has been around almost as long as the automobile itself.

At the turn of the twentieth century, as the automotive age dawned, three power-generating technologies competed for dominance: steam, gasoline, and electricity. In the year 1900, steam was well known as the power source of the industrial revolution, and electricity was widely regarded as the power source of the future, so it was not at all obvious that internal combustion engines burning a fractional distillate of crude petroleum would have any particular edge in this race for the powertrains of America. Indeed, when engineer H. Piper filed the first patent application for a gasoline-electric hybrid motor in 1905, his intention was to use the gas to give a little kick to his perfectly serviceable electric engine. His goal: an engine that could accelerate from 0 to 25 miles per hour in 10 seconds.

Piper achieved his goal. Electric and hybrid-electric engines powered more than 35,000 vehicles sold in 1912. These cars were perfectly adequate for the time, but over the following decade they mostly disappeared from the market, through no fault of their own. The cause of their decline was the spectacular improvements in the cost and performance of gasoline-powered cars. An onslaught of fast and cheap internal combustion cars from Ford, General Motors, and Buick essentially buried the electric and electric-hybrid motors by the 1920s.

Continuing performance improvements in internal combustion engines and inexpensive gas pretty much kept hybrids buried until the oil crises of 1973 and 1979 gave Americans a reason to start thinking about fuel efficiency. Engineers had the motivation to think about fuel-efficient hybrids, but they still lacked the means to make hybrids economically competitive with gas-powered cars, because the performance of gas-electric engines lagged far behind that of gas-powered engines in acceleration, top speed, and cruising range.

Dramatic improvements in electronics and computer technology during the 1990s, however, finally made the hybrid a reality. Advances in battery performance and, most importantly, computer-guided electric power transfer created a car that could drive like a regular car, but do so on half the tank of gas. As another century dawns, perhaps we are entering into a new automotive age.

According to the passage, electric and hybrid cars failed to capture the American automotive market in the early twentieth century because of what factor ?()

A. The improvement in cost and performance of gasoline-powered cars

B. The superior fuel efficiency of hybrid cars

C. The substandard performance of steam-powered cars

D. Consumer fear of being electrocuted by gasoline-electric hybrids

E. Government subsidies for gasoline- and coal-powered cars

单项选择题