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25 these galaxies may constitute an answer to the

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(25) These galaxies may constitute an answer to the long- standing puzzle of the missing baryonic mass in the universe. Baryons—subatomic particles (30) that are generally protons or neutrons—are the source of stellar, and therefore galactic, luminosity, and so their numbers can be estimated based on how (35) luminous galaxies are. How- ever, the amount of helium in the universe, as measured by spectroscopy, suggests that there are far more baryons (40) in the universe than estimates based on galactic luminosity indicate. Astronomers have long speculated that the missing baryonic mass might eventually (45) be discovered in intergalactic space or as some large popu- lation of galaxies that are difficult to detect. -------------------------------------------------------------------------------- Q35: The primary purpose of the passage is to A. describe a phenomenon and consider its scientific significance B. contrast two phenomena and discuss a puzzling difference between them C. identify a newly discovered phenomenon and explain its origins D. compare two classes of objects and discuss the physical properties of each E. discuss a discovery and point out its inconsistency with existing theory Answer: -------------------------------------------------------------------------------- Q36: The author mentions the fact that baryons are the source of stars’ luminosity primarily in order to explain 32
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-------------------------------------------------------------------------------- Q37: It can be inferred from the passage that which of the following is an accurate physical description of typical low-surface-brightness galaxies? ----------------------------------------------------------------------------------------------------------- - Q38: Two centuries ago, Tufe Peninsula became separated form the mainland, isolating on the newly formed Tufe Island a population of Turfil sunflowers. This population’s descendants grow to be, on average, 40 centimeters shorter than Turfil sunflowers found on the mainland. Tufe Island is significantly drier than Tufe Peninsula was. So the current average height of Tufe’s Turfil sunflowers is undoubtedly at least partially attributable to changes in Tufe’s environmental conditions. Which of the following is an assumption on which the argument depends?
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