They examined differences between red squirrels and gray squirrels in the American state of Indiana. The scientists wanted to know how these differences could affect the growth of black walnut (黑胡桃) trees. The black walnut is the nut of choice for both kinds of squirrels. The black walnut tree is also a central part of some hardwood forests.
Rob Swihart of Purdue University did the study with Jake Goheen, a former Purdue student now at the University of New Mexico. The two researchers estimate that several times as many walnuts grow when gathered by gray squirrels as compared to red squirrels. Gray squirrels and red squirrels do not store nuts and seeds in the same way. Gray squirrels bury nuts one at a time in a number of places. But they seldom remember where they buried every nut. So some nuts remain in the ground. Conditions are right for them to develop and grow the following spring. Red squirrels, however, store large groups of nuts above ground. Professor Swihart calls “death traps for seeds”.
Gray squirrels are native to Indiana. But Professor Swihart says their numbers began to decrease as more forests were cut for agriculture. Red squirrels began to spread through the state during the past century.
The researchers say red squirrels are native to forests that stay green all year, unlike walnut trees. They say the cleaning of forest land for agriculture has helped red squirrels invade Indiana. Jake Goheen calls them a sign of an environmental problem more than a cause.
60. The study done by Rob Swihart and Jake Goheen is to ________.
A. find out the living conditions for squirrels B. learn squirrels’ influence on black walnut trees
C. do something to get rid of squirrels D. save the forests in the American state of Indiana
61 The difference between gray squirrels and red squirrels mainly lies in ________.
A. the way they gather the walnut B. the time they have winter sleep
C. the place they have winter sleep D. the place they store the walnuts
62. When Professor Swihart says “death traps for seeds”, he actually means that ________.
A. red squirrels eat more nuts than gray squirrels B. gray squirrels and red squirrels will have severe fights
C. nuts above the ground will not develop into plants D. seeds can be traps for other animals in the forest
63. According to the passage, which of the following is true?
A. The black walnut is equally attractive to both gray and red squirrels.
B. G
ray squirrels do more harm to the forest than red squirrels.
C. Red squirrels and gray squirrels have helped the spread of walnut trees.
D. The cleaning of forest land benefits red squirrels directly.
(C)
Television is a relatively stable advertising medium. In many ways, the television ads today are almost the same to those two decades ago. Most television ads still feature actors, still run 30 or 60 seconds, and still show a product. However, the different medium of the Internet causes unique challenges to advertisers, forcing them to adapt their practices and techniques.
In the early days of Internet marketing, online advertisers used banner (框式广告) and pop-up ads(弹出式广告) to attract customers. These techniques reached large audiences, led to many sales leads, and came at a low cost. However, a small number of Internet users began to consider these advertising techniques annoying. Yet because marketing strategies relying heavily on banners and pop-ups produced results, companies invested growing amounts of money into purchasing these ad types. As consumers became more complicated, frustration with these online advertising techniques grew. Independent programmers began to develop tools that blocked banner and pop-up ads.
A major development in online marketing came with the introduction of pay-per-click ads. Unlike banner or pop-up ads, which originally required companies to pay every time a website visitor saw an ad, pay-per-click ads allowed companies to pay only when an interested potential customer clicked on an ad. More importantly, however, these ads are not affected by the pop-up and banner blockers. As a result of these advantages and the incredible growth in the use of search engines, which provide excellent places for pay-per-click advertising, a great number of companies began turning to pay-per-click marketing. However, as with the banner and pop-up ads, pay-per-click ads came with their shortcomings. When companies began pouring billions of dollars into this emerging medium, online advertising specialists started to notice the presence of what would later be called click fraud (欺诈): representatives of a company with no interest in the product advertised by a competitor click on the competitor’s ads simply to increase the marketing cost of the competitor. Click fraud grew so rapidly that marketers sought to diversify (摆脱) their online positions away from pay-per-click marketing through new mediums.
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