2017年大学英语四级精选试题练习

　　勤奋和智慧是双胞胎，懒惰和愚蠢是亲兄弟。以下是小编为大家搜索整理的2017年大学英语四级精选试题练习，希望能给大家带来帮助!更多精彩内容请及时关注我们应届毕业生考试网!

2017年大学英语四级精选试题练习

　　1、Courses with the numbers 800 or above are open only to graduate students. Certain courses, generally those devoted to introductory material, are numbered 400 for undergraduate students and 600 for graduate students. Courses designed for students seeking a professional degree carry a 500 number for undergraduate students and a 700 munber for graduate students.

　　A full-time graduate student is expected to take courses which total ten to sixteen credit hours. Students holding assistantships are expected to enroll for proportionately fewer hours. A part-time graduate student must register for a minimun of five credit hours.

　　1. In order to be eligible to enroll in Mechanical Engineering 850, a student must be ________.

　　a. a graduate student

　　b. a part-time student

　　c. a full-time student

　　d. an undergraduate student

　　2. If an undergraduate student uses the number 520 to register for an accounting course, what number would a graduate student probably use to register for the same course?

　　a. accounting 520

　　b. accounting 620

　　c. accounting 720

　　d. accounting 820

　　3. A student who register for eight credit hours is a ________.

　　a. full-time student

　　b. graduate student

　　c. part-time student

　　d. non-degree student

　　4. A graduate student may not ________

　　a. enroll in a course numbered 610

　　b. register for only one three-hour course

　　c. register for courses if he has an assistantship

　　d. enroll in an introductory course

　　答案：accb

　　2、There is evidence that the usual variety of high blood pressure is, in part, a familiar disease. Since families have similar genes as well as similar environments, familiar diseases could be due to shared genetic influences, to shared environmental factors, or to both. For some years, the role of one environmental factor commonly shared by families, namely dietary salt (i. e., sodium chloride), has been studied at Brookhaven National Laboratory. These studies suggest that chromic excess salt ingestion can lead to high blood pressure in man and animals. Some individuals, however, and some rats consume large amounts of salt without developing high blood pressure. No matter how strictly all environmental factors were controlled in these experiments, some salt-fed animals never developed hypertension whereas a few rapidly developed very severe hypertension followed by early death. These marked variations were interpreted to result from differences in genetic constitution.

　　By mating is successive generations only those animals that failed to develop hypertension from salt ingestion, a resistant strain (the "R"Strain) has been evolved in which consumption of large quantities of salt fails to influence the blood pressure significantly. In contrast, by mating only animals that quickly develop hypertension from salt, a sensitive strain ("S" strain) has also been developed.

　　The availability of these tow strains permits investgations not heretofore possible. They provide a plausible laboratory model on which to investigate some clinical aspects of the human prototypes of hypertension. More important, there might be the possibility of developing methods by which genetic susceptibility of human beings to high blood pressure can be defined without waiting for its appearance. Radioactive sodium 22 was an important "tool" in working out the characteristics of the sodium chloride metabolism.

　　1. The study of the effects of salt on high blood pressure was carried out ________.

　　a. as members of the same family tend to use similar amounts of salt

　　b. to explore the long-term use of a sodium based substance

　　c. because it was proven that salt caused high blood pressure

　　d. because of the availability of chemically pure salt and its derivatives

　　2. The main difference between "S"and"R" rats is their ________.

　　a. need for sodium 22

　　b. rate of mating

　　c. reaction to salt

　　d. type of blood

　　3. We can infer from the article that sodium 22 can de used to ________.

　　a. control high blood pressure