【正文】 that required no rain and somehow made itpossible for cattle to feed themselves all winter? But the surprising western wild (15)grasses did just that. They had wonderfully convenient features that made themsuperior to the cultivated eastern grasses. Variously known as buffalo grass, gramagrass, or mesquite grass, not only were they immune to drought。s voyages, nearly all earth scientists agree on the theories of plate tectonics and continental drift that explain many of the geological processes that shape the Earth. The cores of sediment drilled by the Glomar Challenger have also yielded (25)information critical to understanding the world39。s surface and drill in very deep waters, extracting samplesof sediments and rock from the ocean floor. (15) The Glomar Challenger pleted 96 voyages in a 15year research program that ended in November 1983. During this time, the vessel logged 600,000 kilometers and took almost 20,000 core samples of seabed sediments and rocks at 624 drilling sitesaround the world. The Glomar Challenger39。s Deep Sea Drilling Project (DSDP). Using techniques first developed for the offshore oil and gas industry. the DSDP39。s core is made of elements that are word speculate in line 24 is closest in meaning to (A) report(B) learn(C) worry(D) hypothesizePassage 2The ocean bottom a region nearly times greater than the total land area of the Earth is a vast frontier that even today is largely unexplored and uncharted. Untilabout a century ago, the deepocean floor was pletely inaccessible, hidden beneath waters averaging over 3,600 meters deep. Totally without light and subjected to intense(5) pressures hundreds of times greater than at the Earth39。s core.(C) It is impossible to go to the Earth39。s core.(B) Scientists aren39。s mantle?(A) Light, solid rock(B) Uniformity of position (C) Dramatically increasing pressure(D) Compressed, incandescent gas phrase gives way to in line 18 is closest in meaning to(A) runs along(B) rubs against(C) turns into(D) floats on word it in line 19 refers to (A) mantle(B) core(C) change(D) depth does the author state in line 22 that the Earth39。s interior for geologis ts?(A) Boreholes(B) Shells(C) Seismic waves(D) Mines word There in line 12 refers to the(A) mantle(B) crust(C) seabed(D) Earth39。F. Although scientists can speculate about its nature, neither humans normachines will ever be able to visit it. word conflicting in line 2 is closest in meaning to(A) controlling(B) outdated(C) opposing(D) important is today39。 at greater depths, high temperatures(15)make the rock behave more like a liquid than a solid. Deeper still, the pressure is evenmore intense, preventing the rock from melting in spite of a higher temperature.Beyond a depth of around 2,900 kilometers, a great change takes place and themantle gives way to the core. Some seismic waves cannot pass through the core andothers are bent by it. From this and other evidence, geologists conclude that the outer(20)core is probably liquid, with a solid center. It is almost certainly made of iron, mixedwith smaller amounts of other elements such as nickel.The conditions in the Earth39。s interior is far from(10)uniform. The continents and the seabed are formed by the crusta thin sphere ofrelatively light, solid rock. Beneath the crust lies the mantle, a very different layer thatextends approximately halfway to the Earth39。s interior. Some geologiststhought that it contained a highly pressed ball of incandescent gas, while others Line suspected that it consisted of separate shells, each made of a different material. Today,(5) well over a century later, there is still little direct evidence of what lies beneath ourfeet. Most of our knowledge of the Earth39。C, while others can grow at 5176。s honor, Hazen named it Streptomyces noursei, and within a year the two scientists knew (20) 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 e from rather modest beginnings.45. What is the main topic of the passage?(A) The lives of Hazen and Brown. (B) The development of a safe fungicide. (C) The New York State Department of Health.(D) The development of penicillin. 46. What can be inferred from the passage about penicillin? (A) It effectively treats fungus infections. (B) It was developed before nystatin.(C) It was developed the Second World War. (D) One of the byproducts is nystatin. 47. Why does the author mention Columbia University in lines 10 and 11? (A) Hazen and Brown developed nystatin there.(B) Brown was educated there. (C) Hazen did research there. (D) It awarded a prize to Hazen and Brown. 48. The word both in line 11 refers to (A) Hazen and Brown (B) Penicillin and streptomycin (C) the Department of Health laboratories at Albany and New York (D) double effect 49. What substance did Brown and Hazen analyze? (A) Dirt (B) Streptomycin(C) Penicillin (D) Bacteria 50. Who was W. B. Bourse? (A) A microbiologist (B) A teacher of Hazen39。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 (15) purified active agents, and shipped them back to New York, where Hazen could study their biological properties. On a 19