Small,portable computers may use liquid crystal displays．

A portable dry chemical fire extinguisher discharges by ______.

A.gravity when the extinguisher is turned upside down

B.pressure from a small CO2 cartridge on the extinguisher

C.air pressure from the hand pump attached to the extinguisher

D.pressure from the reaction when water is mixed with the chemical

A．错误

B．正确

A．错误

B．正确

A.dra？？t

B.compu*er

C.？umor

D.#1not#2

A．of or relating to visual art, especially involving drawing, engraving, or lettering

B．of or relating to, or denoting a visual image

d the fundamental impact of recorded music. Electronic engineering furnishes products which are replaced so【C1】______. It is easy to forget the importance they held at the time of their【C2】______. Before the advent of digital equipment, there were a whole【C3】______ of mechanisms designed to record sound, from the original hand-cranked gramophones,【C4】______ the electric phonographs, the stereo record albums, to the cassette tapes. There are two【C5】______ for these developments: the precision of recording, and the【C6】______ of the equipment. Digital sound engineering is the【C7】______ of industrial efforts. It can【C8】______ the musical sources to the minutest detail and【C9】______ reproduced sounds through portable players. 【C10】______ the continuous wave of new sound facilities, entertainment has changed its form. Before the introduction of mechanical reproduction, it【C11】______ almost impossible to【C12】______ having an entire symphony, performed in a court setting, within a house of small size.【C13】______ classical music, a single household can host a dozen different bands of【C14】______ styles. The delivery of music through the electronic medium now claims high【C15】______ and encourages the prospect of creating a(n)【C16】______ reality. The boundary between reality and representation thus【C17】______ its clear-cut definition; listeners have great difficulty in deciding which is【C18】______, the live source, or the reproduced acoustics. 【C19】______ the distinction between fiction and reality is becoming more and more【C20】______, lifelikeness remains the principle criterion in measuring the effectiveness of sound since the invention of the gramophone.

【C1】

A．quickly

B．gradually

C．slowly

D．abruptly

aps $5 000 or more.【B1】______, it is not uncommon for them to purchase【B2】_______ costing another several hundred dollars. Twenty years ago, computers were【B3】______, but they were very large and extremely expensive. Few, if any,【B4】______purchased computers for home use. Over the years, the price of the "guts" Of a computer its memory—has declined to less than a thousandth of the price per unit of memory that prevailed twenty years ago. This is the main reason why computers cost so much less today than they used to. Moreover,【B5】______improvements have made it possible to【B6】______memory circuitry that is small enough to fit into the portable personal computers that many of us own and use.【B7】______, as the price of computation has declined the average consumer and business have spent more on purchasing computers. 【B8】______, improved agricultural technology, hybrid(杂交)seeds,【B9】______animal breeding, and so on have vastly increased the amount of output a typical farmer can produce. The prices of goods such as meats and grains have fallen sharply relative to the prices of most other goods and services. As agricultural prices have fallen, many households have decreased their total expenses on food. Even though the【B10】______of a product purchased generally increases when its price falls, total expenses on it may decline.

【B1】

, but numerous other dependents as well---grandparents, uncles, aunts and cousions. Such "extended" families were suited for survival in slow paced __1__ societies. But such families are hard to __2__. They are immobile.Industrialism demanded masses of workers ready and able to move off the land in pursuit of jobs, and to move again whenever necessary. Thus the extended family __3__ shed its excess weight and the so-called "nuclear" family emerged-a stripped-down, portable family unit __4__ only of parents and a small set of children. This new style. family, far more __5__ than the traditional extended family, became the standard model in all the industrial counties. Super-industrialism, however, the next stage of eco-technological development, __6__ even higher mobility. Thus we may expect many among the people of the future to carry the streamlinling process, a stePfurther by remaining children, cutting the family down to its more __7__ components, aman and a woman. Two people, perhaps with matched careers, will prove more efficient at navigating through education and social status, through job changes and geographic relocations, than teh ordinarily child-cluttered family.A __8__ may be the postponement of children, rather than childlessness. Men and women today are often torn in __9__ between a commitment to career and a commitment to children. In the future, many __10__ will sidestePthis problem by deferring the entire task of raising children until after retirement.

A)transplant

B)solution

C)gadually

D)transport

E)elemental

F)conflict

G)continually

H)mobile

I)couples

J)agricultural

k)including

L)compromise

M)requires

N)primary

O)consisting