insisted, with good　reasons, that it was the only engine for them. In shallow western rivers the　weight of vessel and　engine was important; a heavy engine added to the problem of navigation. The　high-pressure engine was far lighter in proportion to horsepower, and, with less　than half as many moving parts, was much easier and cheaper to repair. The main　advantages of low-pressure engines were safe　operation and economy of fuel consumption, neither of which meant much in the　West.

　　33 What is the passage mainly about?

　　(A) Steamboat engines in the western United States

　　(B) River travel in the western United States

　　(C) A famous United States inventor

　　(D) The world's first practical steamboat

　　34 What was the Clermont (line 10)?

　　(A) A river

　　(B) A factory

　　(C) A boat

　　(D) an engine

　　35 Who developed the kind of steam engine used on western steamboats?

　　(A) Watt

　　(B) Boulton

　　(C) Fulton

　　(D) Evans

　　36 The word "novel" in line 14 is closest in meaning to

　　(A) fictional

　　(B) intricate

　　(C) innovative

　　(D) powerful

　　37 What opinion of Evans is suggested by the use of the term "unsung hero" in

　　line 14?

　　(A) More people should recognize the importance of his work .

　　(B) More of his inventions should be used today.

　　(C) He should credited with inventing the steam engine.

　　(D) More should be learned about his early lift.

　　38 What does the author imply about Evans?

　　(A) He went to England to learn about steam power.

　　(B) He worked for Fulton.

　　(C) He traveled extensively in the West.

　　(D) He taught himself about steam engines.

　　39 The work "stationary" in line 17 is closest in meaning to

　　(A) single

　　(B) fixed

　　(C) locomotive

　　(D) modified

　　40 The word "they" in line 18 refers to

　　(A) engines

　　(B) mechanized production and steam power

　　(C) possibilities

　　(D) steamboats

　　41 What does the author imply about the western rivers?

　　(A) It was difficult to find fuel near them.

　　(B) They flooded frequently.

　　(C) They were difficult to navigate.

　　(D) They were rarely used for transportation.

　　42 The word "it" in line 23 refers to

　　(A) decade

　　(B) high-pressure engine

　　(C) weight

　　(D) problem

　　43 The word "vessel" in line 24 is closest in meaning to

　　(A) fuel

　　(B) crew

　　(C) cargo

　　(D) craft

　　44 Which of the following points was made by the critics of high-pressure

　　engines?

　　(A) They are expensive to import.

　　(B) They are not powerful enough for western waters.

　　(C) They are dangerous.

　　(D) They weigh too much.　　

　　Questions 45-50

　　Volcanic fire and glacial ice are natural enemies. Eruptions at glaciated　volcanoes typically　destroy ice fields, as they did in 1980 when 70 percent of Mount Saint Helens　ice cover was　demolished. During long dormant intervals, glaciers gain the upper hand cutting　deeply into volcanic cones and eventually reducing them to rubble. Only rarely　do these competing forces of　heat and cold operate in perfect balance to create a phenomenon such as the　steam caves at　Mount Rainier National Park.　Located inside Rainier's two ice-filled summit craters, these caves form a　labyrinth of tunnels　and vaulted chambers about one and one-half miles in total length. Their　creation depends on an　unusual combination of factors that nature almost never brings together in one　place. The　cave-making recipe calls for a steady emission of volcanic gas and heat, a heavy　annual snowfall at an elevation high enough to keep it from melting during the　summer, and a bowl-shaped crater　to hold the snow.　Snow accumulating yearly in Rainier's summit craters is compacted and　compressed into a　dense form of ice called firn, a substance midway between ordinary ice and the　denser crystalline ice that makes up glaciers. Heat rising from numerous　openings (called fumaroles) along the inner　crater walls melts out chambers between the rocky walls and the overlying ice　pack.Circulating　currents of warm air then melt additional opening in the firn ice,eventually　connecting the individual chambers and, in the larger of Rainier's two craters,forming a continuous passageway　that extends two- thirds of the way around the crater's　interior.　To maintain the cave system, the elements of fire under ice must remain in　equilibrium.Enough snow must fill the crater each year to replace that melted　from below. If too much volcanic heat is discharged, the crater's ice pack will　melt away entirely and the caves will vanish along with the　snow of yesteryear. If too little heat is produced, the ice, replenished　annually by winter　snowstorms, will expand, pushing against the enclosing crater walls and　smothering the present　caverns in solid firn ice.　45 With what topic is the passage primarily concerned?

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