2017年托福考试练习巩固试题

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2017年托福考试练习巩固试题

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2017年托福考试练习巩固试题

　　PASSAGE 43

　　(25)

　　Elizabeth Hazen and Rachel Brown copatented one of the most widely acclaimed wonder drugs of the post-Second World War years. Hazen and Brown's work was stimulated by the wartime need to find a cure for the fungus infections that afflicted many military personnel. Scientists had been feverishly searching for an antibiotic toxic enough to kill the fungi but safe enough for human use, since, unfortunately, the new "wonder drugs" such as penicillin and streptomycin killed the very bacteria in the body that controlled the fungi. It was to discover a fungicide without that double effect that Brown, of New York State's Department of Health Laboratories at Albany, and Hazen, senior microbiologist at the Department of Health in New York, began their long-distance collaboration. Based upon Hazen's previous research at Columbia University, where she had built an impressive collection of fungus cultures, both were convinced that an antifungal organism already existed in certain soils.

　　They divided the work. Hazen methodically screened and cultured scores of soil samples, which she then sent to her partner, who prepared extracts, isolated and purified active agents, and shipped them back to New York, where Hazen could study their biological properties. On a 1948 vacation, Hazen fortuitously collected a clump of soil from the edge of W.B. Nourse's cow pasture in Fauquier County, Virginia, that, when tested, revealed the presence of the microorganisms. In farm owner Nourse's honor, Hazen named it Streptomyces Noursei, and within a year the two scientists knew that the properties of their substance distinguished it from previously described antibiotics. After further research they eventually reduced their substance to a fine, yellow powder, which they first named "fungiciden." Then renamed "nystatin" (to honor the New York State laboratory) when they learned the previous name was already in use. Of their major discovery, Brown said lightly that it simply illustrated "how unpredictable consequences can come from rather modest beginnings."

　　1. What is the main topic of the passage ?

　　(A) The lives of Hazen and Brown.

　　(B) The development of a safe fungicide.

　　(D) The development of penicillin.

　　2. What can be inferred from the passage about penicillin?

　　(A) It effectively treats fungus infections.

　　(B) It was developed before nystatin.

　　(D) One of its by-products is nystatin.

　　3. Why does the author mention Columbia University in line 10?

　　(A) Hazen and Brown developed nystatin there.

　　(B) Brown was educated there.

　　(D) It awarded a prize to Hazen and Brown.

　　4. The word "both" in line 11 refers to

　　(A) Hazen and Brown

　　(B) penicillin and streptomycin

　　(D) double effect

　　5. What substance did Brown and Hazen analyze?

　　(A) Dirt

　　(B) Streptomycin

　　(D) Penicillin

　　6. Who was W. B. Nourse?

　　(A) A microbiologist

　　(B) A teacher of Hazen's

　　(D) A farmer

　　参考答案：BBCAA D

　　PASSAGE 44

　　The nervous system of vertebrates is characterized by a hollow, dorsal nerve cord that ends in the head region as an enlargement, the brain. Even in its most primitive form this cord and its attached nerves are the result of evolutionary specialization, and their further evolution from lower to higher vertebrate classes is a process that is far from fully understood. Nevertheless, the basic arrangements are similar in all vertebrates, and the study of lower animals gives insight into the form and structure of the nervous system of higher animals. Moreover, for any species, the study of the embryological development of the nervous system is indispensable for an understanding of adult morphology.

　　In any vertebrate two chief parts of the nervous system may be distinguished. These are the central nervous system (the nerve cord mentions above), consisting of the brain and spinal cord, and the peripheral nervous system, consisting of the cranial, spinal, and peripheral nerves, together with their motor and sensory endings. The term "autonomic nervous system" refers to the parts of the central and peripheral systems that supply and regulate the activity of cardiac muscle, smooth muscle, and many glands.

　　The nervous system is composed of many millions of nerve and glial cells, together with blood vessels and a small amount of connective tissue. The nerve cells, or "neurons", are characterized by many processes and are specialized in that they exhibit to a great degree the phenomena of irritability and conductivity. The glial cells of the central nervous system are supporting cells collectively termed "neuroglia". They are characterized by short processes that have special relationships to neurons, blood vessels, and connective tissue. The comparable cells in the peripheral nervous system are termed "neurilemmal" cells.

　　1. What does the passage mainly discuss?

　　(A) The parts of a neuron

　　(B) The structure of animals' nerve

　　(D) The development of the brain

　　2. According to the passage , the nerve cord of vertebrates is

　　(A) large

　　(B) hollow

　　(D) embryological

　　3. The author implies that a careful investigation of a biological structure in an embryo may

　　(A) Improved research of the same structure in other species

　　(B) A better understanding of the fully developed structure

　　(D) A method by which scientists can document the various stages of development