Whileintegrasedeletesanimmunecell'sgeneticmaterialandreplacesitwithitsown,itactslike________inawordprocessor.

In selecting a material, the engineer’s interest is in its properties，which determine how it will perform under the loads and condition____it is subject.

Paragraphs2and3explain________.

Scattered through the seas of the world are billions of tons of small plants and animals called plankton. Most of these plants and animals are too small for the human eye to see. They drift about lazily with the currents, providing a basic food for many larger animals. Plankton has been described as the equivalent of the grasses that grow on the dry land continents, and the comparison is an appropriate one. In potential food value however, plankton far outweighs that of the land grasses. One scientist has estimated that while grasses of the world produce about 49 billion tons of valuable carbohydrates each year. The sea’s plankton generates more than twice as much.

Despite its enormous food potential, little effort was made until recently to farm plankton as we farm grasses on land. Now marine scientists have at last begun to study this possibility, especially as the sea’s resources loom even more important as a means of feeding an expanding world population.

No one yet has seriously suggested that “planktonburgers” may soon become popular around the world. As a possible farmed supplementary food source, however, plankton is gaining considerable interest among marine scientists.

One type of plankton that seems to have great harvest possibilities is a tiny shrimplike creature called krill. Growing to two or three inches long, krill provide the major food for the giant blue whale, the largest animal ever to inhabit the Earth. Realizing that this whale may grow 100 feet and weigh 150 tons at maturity, it is not surprising that each one devours more than one ton of krill daily.

Krill swim about just below the surface in huge schools sometimes miles wide, mainly in the cold Antarctic. Because of their pink color, they often appear as a solid reddish mass when viewed from a ship or from the air. Krill are very high in food value. A pound of these crustaceans contains about 460 calories—about the same as shrimp or lobster, to which they are related.

If the krill can feed such huge creatures as whales, many scientists reason, they must certainly be contenders as new food source for humans.

1.Which of the following best portrays the organization of the passage?

A.The author presents the advantages and disadvantages of plankton as a food source.

B.The author quotes public opinion to support the argument for farming plankton.

C.The author classifies the different food sources according to amount of carbohydrate.

D.The author makes a general statement about plankton as a food source and then moves to a specific example.

2.According to the passage, why is plankton regarded to be more valuable than land grasses?

A.It is easier to cultivate.

B.It produces more carbohydrates.

C.It does not require soil.

D.It is more palatable.

3.Why does the author mention “planktonburgers”?

A.To describe the appearance of one type of plankton.

B.To illustrate how much plankton a whale consumes.

C.To suggest plankton as a possible food sources.

D.To compare the food values of beef and plankton.

4.What is mentioned as one conspicuous feature of krill?

A.They are the smallest marine animals.

B.They are pink in color.

C.They are similar in size to lobsters.

D.They have grass like bodies.

5.The author mentions all of the following as reasons why plankton could be considered a human food source except that it is ___.

A.high in food value.

B.in abundant supply in the oceans.

C.an appropriate food for other animals.

D.free of chemicals and pollutants.

If the old maxim that the customer is always right still has meaning, then the airlines that ply the world’s busiest air route between London and Paris have a flight on their hands.

The Eurostar train service linking the UK and French capitals via the Channel Tunnel is winning customers in increasing numbers. In late May, it carried its one millionth passenger, having run only a limited service between London, Paris and Brussels since November 1994, starting with two trains a day in each direction to Paris and Brussels. By 1997, the company believes that it will be carrying ten million passengers a year, and continue to grow from there.

From July, Eurostar steps its service to nine trains each way between London and Paris, and five between London and Brussels. Each train carries almost 800 passengers, 210 of them in first class.

The airlines estimate that they will initially lose around 15%-20% of their London-Paris traffic to the railways once Eurostar starts a full service later this year (1995), with 15 trains a day each way. A similar service will start to Brussels. The damage will be limited, however, the airlines believe, with passenger numbers returning to previous levels within two to three years.

In the short term, the damage caused by the 1 million people-levels traveling between London and Paris and Brussels on Eurostar trains means that some air services are already suffering. Some of the major carriers say that their passenger numbers are down by less than 5% and point to their rivals-Particularly Air France-as having suffered the problems. On the Brussels route, the railway company had less success, and the airlines report anything from around a 5% drop to no visible decline in traffic.

The airlines’ optimism on returning traffic levels is based on historical precedent. British Midland, for example, points to its experience on Heathrow Leeds Bradford service which saw passenger numbers fold by 15% when British Rail electrified and modernized the railway line between London and Yorkshire. Two years later, travel had risen between the two destinations to the point where the airline was carrying record numbers of passengers.

1.British airlines confide in the fact that__.

A.they are more powerful than other European airlines.

B.their total loss won’t go beyond a drop of 5% passengers.

C.their traffic levels will return in 2-3 years.

D.traveling by rail can never catch up with traveling by air.

2.The author’s attitude towards the drop of passengers may be described as__.

A.worried.B.delightedC.puzzled.D.unrivaled.

3.In the passage, British Rail (Para 6) is mentioned to__.

A.provide a comparison with Eurostar.

B.support the airlines’ optimism.

C.prove the inevitable drop of air passengers.

D.call for electrification and modernization of the railway.

4.The railway’s Brussels route is brought forth to show that__.

A.the Eurostar train service is not doing good business.

B.the airlines can well compete with the railway.

C.the Eurostar train service only caused little damage.

D.only some airlines, such as Air France, are suffering.

5.The passage is taken from the first of an essay, from which we may well predict that in the following part the author is going to__.

A.praise the airlines’ clear-mindedness.

B.warn the airlines of high-speed rail services.

C.propose a reduction of London/Paris flights.

D.advise the airlines to follow British Midland as their model.