单选题. ①The recently announced discovery of the first known planet orbiting a pulsar (the ultradense, pulsating remnant off the supernova explosion of a star) turned out to be based on faulty data. ②Had this discovery been confirmed, theorists would have had difficulty accounting for the existence of such a planet. ③The supernova would certainly have destroyed any preexisting planets. ④This particular pulsar is relatively young, allowing little time for a new planet to have coalesced, and it rotates relatively slowly, implying that it has not interacted with any nearby star since the supernova. ①But newer evidence of a different pulsar with planets is more promising. ②This is a rapidly spurring ''millisecond pulsar" thought to be a much older object that has pulled gaseous material from a stellar neighbor, causing its rotational speed to increase. ③Leftover, unconsumed gas around such a pulsar could, in theory, coalesce into planets. ④Or the pulsar's radiation might have vaporized a companion star, providing new material for planetary formation.4. The primary purpose of the passage is to ______

单选题某一矩形的一条边是4+3S，另一条边是8-S，问矩形的周长不可能是下面哪一个?

单选题. ①The border decoration in medieval manuscripts referred to as pen flourishing reached great artistic heights in the northern Netherlands in the 1400s. ②The regional variants in form that evolved make flourishing a useful tool for localizing and roughly dating manuscripts. ③When the first printed books appeared in that region, many copies were still traditionally decorated by hand with such flourishing. ④Since books' publication can usually be dated with far more accuracy than manuscripts, studying these decorations in early printed books might lead to a more precise dating of the penwork in manuscripts. ⑤It is of less help in localizing the flourishing. ⑥Upon completion, copies of printed books were often sold unadorned, to be decorated elsewhere as commissioned by their buyers.13. Which of the following best describes the function of the highlighted sentence? ______

单选题. ①Ecologists study how millions of species share the world, rather than take on the whole planet at once; they generally focus on a single ecosystem, be it a prairie, a tidal flat, or a sand dune. ②Even within those limits, they are frustrated by porous frontiers. ③As a result, ecologists have done some of their most important work on islands, nature's own isolated laboratories, which may be colonized only a few times over the course of millions of years. ④On them, ecologists have figured out how the size of a given habitat determine how many species it can support. ⑤They have then applied that knowledge to the mainland, showing how fragmented ecosystems become like archipelagoes, where extinctions can strike.38. It can be inferred that the term ''porous frontiers" is used to refer to ______

单选题. ①The physicist Wallace Sabine pioneered the scientific study of architectural acoustics when he was asked in 1895 to fix a university lecture hall in which the echo of a speaker's words rendered them unintelligible. ②He found that the length of time it takes a sound's echo to decay is determined by the absorption of the sound's original energy by surrounding material. ③By hanging panels of sound-absorbing felt on the walls, Sabine reduced the echo enough to make the hall usable. ④And the data he compiled yielded a mathematical formula for the relationship between a room's echo duration, its quantity and quality of sound-absorbing materials, and its spatial volume.19. Which of the following can be inferred about the 'university lecture hall' mentioned in the passage? ______

单选题. ①Favorable environments do not necessarily lead to the occurrence of plant cultivation. ②South China is warmer and moister than North China and the Yangtze Basin, with wild rice and highly abundant natural resources. ③Yet archaeological data indicate that cereal cultivation did not occur in this region until approximately 7,000 to 6,500 years ago. ④This cultivation was likely a result of cultural contact with and expansion from the Yangtze Basin. ⑤Clearly, environmental factors were important for the occurrence of cultivation in China, but were not the absolute determining factors. ⑥While incipient cultivation might occur in areas of relatively abundant resources, it may not occur in areas of very abundant resources, such as South China, where foraging might be a more efficient way of life.38. The author implies which of the following about natural resources in South China prior to 6,500 years ago? ______

单选题. ①George Milner cites three primary problems with the labeling of Cahokia, the large archaeological site by the Mississippi River, as a state rather than a chiefdom. ②First, finds at Cahokia are essentially similar to finds at other Mississippian chiefdoms, except that the amount of earth moved in building the mounds at Cahokia was greater than elsewhere. ③Second, fewer people lived at Cahokia than is commonly estimated (Milner estimates that there were only a few thousand inhabitants, more common estimates are 10,000 or 20,000 inhabitants); therefore, extensive taxes, trade, and tribute were not necessary to support them. ④Finally, while there is evidence of extensive earth movement, craftwork, trade, and elite at Cahokia, this does not indicate that Cahokia was politically centralized, economically specialized, or aggressively expansionistic.26. The primary purpose of the passage is to ______

单选题 ①Matisse's art

单选题If 5＜x＜10 and 0＜y＜32, which of the following gives all possible values of xy?

单选题. ①Although Elizabeth Stuart Phelps' novel Doctor Zay (1882) dominates critical discussion of Phelps' interest in woman doctors, preceding it were many little-known writings by Phelps. ②These writings underscored the achievements of already established women doctors, the imperative of medically educating and training women in the face of pernicious resistance, and the medical woman's symbolic value as an agent of healing in post-Civil War America. ③An exploration of this largely overlooked early prose demonstrates that Phelps played an instrumental role in legitimizing the American medical woman during a crucial earlier period when the number of women doctors in the United States increased substantially, but the woman doctor remained perhaps the most controversial new presence on the nation's occupational landscape.13. It can be inferred that the author of the passage would be likely to agree with which of the following statements about Phelps' writing? ______

单选题一个长方体形木盒子的长、宽、高分别为6，8，10；一个圆柱形罐头被放置在长方体形盒子中，问在所有的罐头中有最大体积罐头的底面半径是多少?

单选题. ①The occurrence of dense aggregations of the fruit-bearing tree Brosimum alicastrum on or near Maya ruin complexes in Central America was initially interpreted as evidence of ancient Maya silviculture, i.e., the stands were relics of orchards planted by the Maya. ②Later work, however, suggested that the stands resulted from the Artibeus bats that roost among the ruins. ③The bats fly to the forest, collect the fruit, bring it back to their roost, eat the fruit, and then discard the undamaged seed. ④The continual input of bat-dispersed seed has maintained the clumps of B. alicastrum around ruins for many hundreds of years. ①This observation, however, does not negate the possibility that B. alicastrum was used and managed by the Maya. ②In fact, if we examine the behavior, rather than the density or location, of these tree populations, we are presented with strong evidence of deliberate genetic improvement. ③This is especially notable in the B. alicastrum trees that cluster around the Maya ruins at Tikal in Guatemala: these trees' productivity is almost twice that of trees in Veracruz, Mexico, under almost identical environmental conditions.13. "The continual input of bat-dispersed seed" is mentioned in the passage as part of an explanation for ______

单选题18. The pepper Capsicum chinense grows as a native wild plant only in South America. Birds swallow the pepper's fruit whole, thereby providing the plant with its means of distributing seeds. Domesticated varieties of C.chinense grow in the Caribbean islands as well as in South America. Although it is unknown just when C.chinense was introduced into the islands, the introduction of the species was probably the result of human activity, because ______. Which of the following most logically completes the argument? ______

单选题If the price of the clothes increases from $20 to $25, what is the percent increase in price?

单选题There are 30 pairs of socks in a drawer, 60％ of the socks are red and the rest are blue. What is the minimum pairs of socks that must be taken from the drawer without looking in order to be certain th

单选题数列{a1，a2，…，an，…}，a1=5，a2=10，an+1=anaan-1，问第几项起就至少有5百万位数字?

单选题 ① When Earth formed 4.6 billion years ago