单选题When - of a certain number is subtracted from the number and then this difference is added with 20, the result is the original number. What is the original number?

单选题. ①Most seismologists assume that following a major earthquake and its aftershocks, the fault (a break in Earth's crust where pressure can trigger an earthquake) will remain quiet until stresses have time to rebuild, typically over hundreds or thousands of years. ②Recent evidence of subtle interactions between earthquakes may overturn this assumption, however. ③According to the stress-triggering hypothesis, faults are unexpectedly responsive to subtle stresses they acquire as neighboring faults shift. ④Rather than simply dissipating, stress relieved during an earthquake travels along the fault, concentrating in sites nearby; even the smallest additional stresses may then trigger another quake along the fault or on a nearby fault. ⑤Although scientists have long viewed such subtle interactions as nonexistent, the hypothesis has explained the location and frequency of earthquakes following several destructive quakes in California, Japan, and Turkey.39. According to the passage, which of the following is an assumption that may be invalidated by recent seismological evidence? ______

单选题What is the total number of integers between 1 00 and 300 that are divisible by 3?

单选题一个矩形长宽分别为80，50，问两条边各增加多少时矩形面积是5400?

单选题. ① MacArthur and Wilson suggested that the biodiversity of an island will vary in direct proportion to a function of the island's size (i.e., larger islands can support a greater number of species) and in inverse proportion to a function of its distance from the mainland (i.e., many remote islands will tend to support fewer species). ②Reduced biodiversity in an island context is likely to require significant adaptation on the part of colonizing human populations. ③Evans argues that this limitation makes islands ideal laboratories for the study of human adaptations to the natural environment, whilst Renfrew and Wagstaff, in the introduction to their study of Melos, focus on this limitation in biodiversity as a "significant characteristic of the island ecosystem." ④For human communities, however, this limitation may potentially be offset by other factors. ⑤The reduced biodiversity of an island ecosystem applies only to terrestrial resources: the resources of the sea will be as rich as on any other coastal area, and may be equally important to human communities. ⑥A small island such as Malta or Melos allows all communities direct access to the sea, providing an important nutritional "safety net," as well as an element of dietary diversity, which may actually give island communities an advantage over their landlocked counterparts. ⑦Islands may also have specific nonbiological resources (such as obsidian on Melos), which may be used in exchange with communities on other islands and adjacent mainlands.35. The primary purpose of the passage is to ______

单选题18. Biologists studying wild monkeys sometimes need the genetic material DNA from a particular monkey to determine the animal's parentage. Until recently, DNA could be extracted only from blood. Collecting a blood sample required tranquilizing the donor animal. Now DNA can be extracted from hair. Monkeys shed large quantities of hair in places where they sleep. Therefore, researchers will now be able to determine the parentage of individual monkeys from DNA without tranquilizing the monkeys. Which of the following is an assumption on which the argument depends? ______

单选题如果某一自然数除了1之外只有2个因子，则这个自然数必为：

单选题. ①One of the reasons why many early British colonies in North America failed amid the New World's abundance was that the settlers' mindset prevented them from living like the native inhabitants. ②From Native Americans, the settlers learned such skills as building brushwood weirs to trap fish, but they did not adopt the real key to success: mobility. ③The whole intellectual foundation of European civilization was fixity—a worldview profoundly different from that of Native Americans, who moved in response to changing food resources. ④Settlers were drawn to North America by tales of its extraordinary abundance, not realizing that abundance is seasonal. ⑤Culture and ecological knowledge allowed Native Americans to exploit different food sources at different time of year.3. The author suggests which of the following about the early British colonies in North America that failed? ______

单选题. ①Ralph Ellison was passionately interested in the visual arts. ②He immersed himself in Harlem's art scene in the 1930s, even apprenticing with sculptor Richmond Barthé for a time. ③Yet he was wary of projects aiming to provide a visual rendering of his novel Invisible Man. ④He reluctantly allowed Franklin Library to publish two illustrated versions of the novel but found the results disappointing and repeatedly rejected proposed film versions of the book. ⑤Despite his involvement in visual arts, Ellison insisted that only language could capture the complexity of American identity. ⑥This complexity consisted of the tension arising from the collision of the United States' written ideals, as outlined in the founding documents, and the historical and contemporary experiences molding the national consciousness.27. It can be inferred that the author mentions Ellison's apprenticeship with Richmond Barthé primarily in order to ______

单选题 ①In recent decades

单选题Quantity A: k is an integer between 1 and 100, inclusive what is probability that k×k+1×k+2×k+3×k+4 is divisible by 20Quantity B: 1

单选题今年5月，上海某家汽车制造厂上线了人们期盼已久的新轿车，在这些轿车中，有20％是红色的，80％是蓝色的；有25％的车排放量是1.6升，有75％的车排放量是1.8升。如果在100辆轿车中有10辆车是红色并且排放量为1.6升，那么有多少辆车是蓝色并且排放量为1.8升?

单选题A是一个由5个不相同的正整数组成的集合，B是一个由4个不相同的正整数组成的集合，并且B是A的子集。问A、B的下面哪一个是不可能相同的?

单选题. ①Until around 1930 few United States Civil War historians paid much attention to Southerners who opposed the 1861-1865 secession from the United States by a confederacy of Southern states. ②Southern historians clung instead to a notion of the South's unanimity in the face of Northern aggression. ③Only when scholars such as Lonn decided to examine this side of the war did historian of the Confederacy begin to recognize the existence of Southerners loyal to the Union (Unionists). ④While these early historians of Southern dissent broke new ground, they also reproduced Confederate authorities' negative view of loyalists as shady characters driven by dubious motives. ⑤Even Tatum, who took a largely sympathetic attitude toward loyalists, tended to lump them into nebulous categories, offering broad generalizations that ignored the particulars of Unionists' identities and experiences. ①This early-twentieth-century historiography nonetheless represented the leading research on dissent in the South until the 1960s and 1970s. ②Spurred by the advent of social historical methods, a new generation of historians found Unionists interesting as manifestations of the Confederacy's internal weaknesses. ③Focusing on the Appalachian Mountain and upper South regions of the Confederacy, these scholars argued that there was a profound divide among Southern Whites between those who benefited economically from slave-run plantations and those who did not. ④One such historian was Escott, who emphasized regional and economic conflict among Southerners. ⑤Escott cast Unionists and other dissenters as mountaineers who could not, by reason of economic and social alienation, identify with the proslavery Southern cause. ⑥This theme has heavily influenced the work of subsequent scholars, who commonly place Unionists at the extreme end of a continuum of class-based Confederate disaffection that was ultimately responsible for the South's collapse. ⑦Because the driving force behind such inquiries into loyalist history has been a desire to explain Confederate ideology, politics, and defeat, emphasis has been placed on the ways loyalist Southerners diverged from the political and economic mainstream of Confederate nationalism. ①Only recently have some Civil War historians begun to make Unionists and their experiences, rather than the Confederate state, the center of inquiry. ②These scholars have done intensive community and local studies of dissenting groups that take into account a range of social and cultural, as well as military and political, factors at work on the Southern home front. ③Hoping to better understand who remained loyal to the Union during the war, these historians have sought to explain the Civil War's underlying character, dimensions, and impact in particular counties or towns, especially in the upper South and Appalachia. ④This relatively new trend has stressed the particular, delved into the complexities of political allegiances on the home front, and, as Sutherland notes, highlighted "the gritty experience of real people."42. The primary purpose of the passage is to ______

单选题 ①According to von Kárman

单选题. ①Many scholars have argued that government investment in manufacturing in the southern United States during the Second World War spurred a regional economic boom that lasted into the postwar period. ②But much of this investment went to specialized plants, many of them unsuitable for postwar production. ③Large-scale, wartime government funding led to a massive increase in the number and scale of munitions facilities. ④By the war's end, 216 munitions establishment costing more than $3.5 billion had been built, many of them located in the south. ⑤Indeed, according to one estimate, more than 70 percent of federally financed manufacturing construction capital in Alabama, Arkansas, Mississippi, and Tennessee went into munitions plants. ①Even in the northern regions with strong prewar manufacturing economics, these plants were difficult to deal with once the imperative of war had been removed. ②In the south few industrialists had the capacity or desire to transform these factories to a peacetime function. ③Accordingly, at war's end almost all of the southern munitions facilities were shut down, placed on standby, operated at a very low capacity, or converted to nonmanufacturing functions, usually storage. ④Although some reopened a few years later for use during the Korean War, the impact of the special plants on the South's postwar economy was marginal at best.35. The primary purpose of the passage is to ______

单选题 ①African American drama has, until recently

单选题gx=x2-x-1 and fx=gx+2Quantity A: f-1Quantity B: f1

单选题 ①Based on evidence from tree rings