多选题If a supernova (the explosion of a massive star) triggered star formation from dense clouds of gas and dust, and if the most massive star to be formed from the cloud evolved into a supernova and triggered a new round of star formation, and so on, then a chain of star-forming regions would result. If many such chains were created in a differentially rotating galaxy, the distribution of stars would resemble the observed distribution in a spiral galaxy. This line of reasoning underlies an {{U}}exciting{{/U}} new theory of spiral-galaxy structure. A computer simulation based on this theory has reproduced the appearance of many spiral galaxies without assuming an underlying density wave, the hallmark of the most widely accepted theory of the large-scale structure of spiral galaxies. That theory maintains that a density wave of spiral form sweeps through the central plane of a galaxy, compressing clouds of gas and dust, which collapse into stars that form a spiral pattern. The author's attitude toward the new theory of spiral-galaxy structure can best be described as A. euphoric. B. enthusiastic. C. concerned. D. critical. E. disputatious.

多选题Atfirstthechildrenwere______,butasthemorningprogressedtheybegantolaughandtalkeagerly.A.ostentatiousB.C.reservedD.puerileE.reticentF.solicitous

多选题No longer narrowly preoccupied with their own national pasts, historians are increasingly ______ in that they often take a transnational perspective.

多选题Amanita bisporigera, a variety of destroying angel mushroom, is so ______ that it can be ______ if consumed.

多选题Wanting to appear both ______ and ______, the official tried to cultivate an authoritative yet solicitous public image.

多选题Studies of ______ of turtles are sometimes ______ by the fact that the subjects live so long that researchers retire before the studies can be completed.

多选题Elephants have a sense of smell that is remarkably ______: they can reportedly smell water up to several miles away.

多选题Staring at the abstract painting, Edna could not understand how SO many of her fellow museumgoers could pretend to ______ its meaning, when to her its message was so opaque.

多选题By the end of the long, arduous hike, Chris was walking with a ______ gait, limping slowly back to the campsite.

多选题The corporation"s code of ethics is ludicrous; its principles are either ______, offering clichés in lieu of guidance，or so unspecific as to make any behavior ______.

多选题The mayor is renowned for her ______ temperament, she can be warm and talkative one moment, aloof and supercilious the pext.

多选题The most objectionable passages in the novel were ______ at the insistence of the censors.

多选题Efforts are finally being made to ______ the traffic congestion that plagues the downtown area.

多选题Some recent historians have argued that life in the British colonies in America from approximately 1763 to 1789 was marked by internal conflicts among colonists. {{U}}Inheritors of some of the viewpoints of early twentieth-century Progressive historians such as Beard and Becker, these recent historians have put forward arguments that deserve evaluation.{{/U}} The kind of conflict most emphasized by these historians is class conflict. Yet with the Revolutionary War dominating these years, how does one distinguish class conflict within that larger conflict? Certainly not by the side a person supported. The author most likely refers to "historians such as Beard and Becker" in order to: A. isolate the two historians whose work is most representative of the viewpoints of Progressive historians. B. emphasize the need to find connections between recent historical writing and the work of earlier historians. C. make a case for the importance of the views of the Progressive historians concerning eighteenth-century American life. D. suggest that Progressive historians were the first to discover the particular internal conflicts in eighteenth-century American life mentioned in the passage. E. point out historians whose views of history anticipated some of the views of the recent historians mentioned in the passage.

多选题The serious purpose of the paper-airplane flying contest, which attracted many novel and sometimes truly ______ entries, was to determine whether any ______ aerodynamic designs could be discovered.

多选题The beauty of Mount McKinley is usually cloaked: clouds ______ the summit nine days out of ten.

多选题After several months of training, the ______ young spaniel was finally ______ enough to be walked safely without a leash.

多选题The ______ of the scientist"s rebuttal of the hypothesis was startling even in the notoriously ______ world of nineteenth-century geology.

多选题Since establishing the Children"s Defense Fund in 1973, Marian Wright Edelman has been an ______ advocate, steadfast and constant.

多选题The ______ nature of the virus allows it to continually change its form and thus go undetected by the body"s immune system.