本题共有三段短文，每段短文后面有三至四道小题，共计十道小题。每道小题都有四个选择项。找出你认为正确的答案，并把其字母填在题前的括号内。（20分）

Passage 1

Researchers have found that REM(rapid eye movement) sleep is important to human beings.Thistype of sleep generally occurs four or five times during one night of sleep,lasting five minutesto forty mimutes for each occurrence.The deeper a person's sleep becomes,the longer the periodsof rapid eye movement.

There are physical changes in the body to show that a person has changed from NREM(non-rapid eye movement) to REM sleep.Breathing becomes faster,the heart rate increases,and,as the name implies,the eyes begin to move quickly.

Accompanying these physical changes in the body is a very important characteristic of REM sleep.It is during REM sleep that a person dreams.

Passage 2

Eating habits change from generation to generation.Before scientists learned about vitamins and other constituents of food, such as proteins and carbohydrates(碳水化合物),people believed in eating large quantities of food and were not concerned so much about a balanced diet. A hearty eighteenth century meal could consist of as many as twenty courses and would probably knock out many of us today! The Romans were famous for their enormous feasts and insatiable appetites.

In the year 2020 people's eating habits may be just as surprising but in a very different sort of way. With a world-wide growth in population, food production will become exclusively mechanical and scientific. There may well be an end to food as we know it today. Meals, as we know them may become a thing of the past. Food constituents and vitamins may be taken in the form of capsules(胶囊), tablets and pills. The thought of these highly artificial food constituents replacing present day foods may not be very attractive, but they may be the answer to food shortage and world famine.

Passage 3

Today we do not measure the speed of computer functions in minutes,or in seconds,or even in hundredths(1/100) or thousandths(1/1000) of seconds. We measure the speed of computers in billionthsof seconds. We call one billionth of a second a nansecond.

Computers were not always so fast, of course. In fact, at one time, the human mind could perform calculations faster than a computer. Let us look briefly at the development of the computer. We will see that the Computer Revolution happened only when computers developed their incredible speed.

In 1833, Charles Babbage built his "analytical engine", the first computing machine. His colleague, Augusta Ada, the Countess of Lovelace, continued Babbage's work. She became the first programmer in history. Fifty years later, Herman Hollerith designed a machine that counted automatically. This machine was used to count the number of people in the United States for the 1890 census. It used a system of punch cards. Hollerith's company,by the way, eventually became IBM(International Business Machines).

The first large digital computer was built by IBM in 1944. It was called the Mark I. Then in 1947,IBM built the Mark II.Today we cannot imagine how slow these computers were,just as we cannot imagine how fast modern computers were, just as we cannot imagine how fast modern computers are. These computers needed one or two seconds to perform one calculation.In these same years, electronic computers developed.They were much faster than the huge, slow Mark I and Mark II. ENIAC is the name of the first all-electronic computer, built in 1944 and 1945. The world was amazed to learn the speed of this computer:5,000 additions per second,and 300 multiplications per second. Today we smile at these "slow" speeds.

Then in 1960 the real"revolution" began with the introduction of integrated circuits. Today,thousands of transistor circuits can fit on one small silicon chip. As a result, we now measure the speed of computers in nanoseconds.