45. if operation migration is successful, whooping cranes will

　　a. learn to migrate on their own

　　b. follow airplanes south every year

　　c. live in canada all year round

　　d. be unable to fly back

　第5部分：补全短文(第46~50题，每题2分，共10分)：下面的短文有5处空白，短文后有6个句子，其中5个取自短文，请根据短文内容讲其分别放回原有位置，以恢复文章面貌。

　　the tough grass that sweetens our lives

　　sugar cane was once a wild grass that grew in new guinea and was used by local people for roofing their houses and fencing their gardens. gradually a different variety evolved which contained sucrose (蔗糖) and was chewed on for its sweet taste. over time, sugar cane became a highly valuable commercial plant, grown throughout the world. ______(46)

　　sugar became a vital ingredient in all kinds of things, from confectionery(糖果点心) to medicine, and, as the demand for sugar grew, the industry became larger de more profitable. ______(47) many crops withered(枯萎) and died, despite growers attempts to save them and there were fears that the health of the plant would continues to deteriorate.

　　in the 1960s, scientists working in barbados looked for ways to make the commercial species stronger and more able to resist disease. they experimented with breeding programs, mixing genes from the wild species of sugar cane, which tends to be tougher, with genes from the more delicate, commercial type. ______(48) this sugar cane is not yet ready to be sold commercially, but when this happens, it is expected to be incredibly profitable for the industry.

　　_______(49) brazil, which produces one quarter of the world’s sugar, has coordinated an international project under professor paulo arrudo of the universidade estaudual de campinas in sao paulo. teams of experts have worked with him to discover more about which parts of the genetic structure of the plant are important for the production of sugar and its overall health.

　　despite all the research, however, we still do not fully understand how the genes in sugar cane. ______(50) this gene is particularly exciting because it makes the plant resistant to rust, a disease which probably originated in india, but is now capable of infecting sugar cane across the world. scientist believe they will eventually be able to grow a plant which cannot be destroyed by rust.

　　a. the majority of the world’s sugar now comes from this particular commercial species.

　　b. unfortunately, however, the plant started to become weaker and more prone to disease.

　　c. eventually, a commercial plant was developed which was 5 percent sweeter than before, but also much stronger and less likely to die from disease.

　　d. since the 1960s, scientists have been analyzing the mysteries of the sugar cane’s genetic code.

　　e. one major gene has been identified by dr angelique d’ hont and her team in montpelier, france.

　　f. sugar cane is now much more vigorous and the supply of sugar is therefore more guaranteed.

　　参考答案：a、 b 、c 、d 、e

第6部分：完形填空(第52~65题，每题1分，共15分)下面的短文有15处空白，请根据短文内容为每处空白确定1个最佳选项。

　　teaching and learning

　　many teachers believe that the responsibilities for learning lie with the student. if a long reading assignment is given, instructors expect students to be familiar with the 1____(information)____ in the reading even if they do not discuss it in class or take an examination. the 2____(ideal)____ student is considered to be one who is motivated to learn for the sake of 3____(learning)____ , not the one interested only in getting high grades. sometimes homework is returned 4____(with)____ brief written comments but without a grade. even if a grade is not given, the student is 5____(responsible)____ for learning the material assigned. when research is 6(assigned) , the professor expects the student to take it actively and to complete it with 7____(minimum) ____guidance. it is the student’s responsibility to find books, magazines, and articles in the library. professors do not have the time to explain 8____(how)____ a university library works; they expect students 9____(particularly)____ graduate students to exhaust the reference 10____(sources)____ in the library. professors will help students who need it, but 11____(prefer____) that their students should not be 12(too) dependent on them. in the united states professors have many other duties 13____(besides)____ teaching, such as administrative or research work. therefore, the time that a professor can spend with a student outside of class is 14____(limited) ____. if a student has problems with classroom work, the student should either 15____(approach) ____a professor during office hours or make an appointment.