The Black Death, a severe epidemic that ravaged fourteenth-century Europe, has intrigued scholars ever since Francis Gasquet's 1893 study contending that this epidemic greatly intensified the political and religious upheaval that ended the Middle Ages. Thirty-six years later, historian George Coulton agreed but, paradoxically, attributed a silver lining to the Black Death: prosperity engendered by diminished competition for food, shelter, and work led survivors of the epidemic into the Renaissance and subsequent rise of modern Europe.
In the 1930s, however, Evgeny Kosminsky and other Marxist historians claimed the epidemic was merely an ancillary factor contributing to a general agrarian crisis stemming primarily from the inevitable decay of European feudalism. In arguing that this decline of feudalism was economically determined, the Marxist asserted that the Black Death was a relatively insignificant factor. This became the prevailing view until after the Second World War, when studies of specific regions and towns revealed astonishing mortality rates ascribed to the epidemic, thus restoring the central role of the Black Death in history.
This central role of the Black Death (traditionally attributed to bubonic plague brought from Asia) has been recently challenged from another direction. Building on bacteriologist John Shrewsbury's speculations about mislabeled epidemics, zoologist Graham Twigg employs urban case studies suggesting that the rat population in Europe was both too sparse and insufficiently migratory to have spread plague. Moreover, Twigg disputes the traditional trade-ship explanation for plague transmissions by extrapolating from data on the number of dead rats aboard Nile sailing vessels in 1912. The Black Death, which he conjectures was anthrax instead of bubonic plague, therefore caused far less havoc and fewer deaths than historians typically claim.
Although correctly citing the exacting conditions needed to start or spread bubonic plague, Twigg ignores virtually a century of scholarship contradictory to his findings and employs faulty logic in his single-minded approach to the Black Death. His speculative generalizations about the numbers of rats in medieval Europe are based on isolated studies unrepresentative of medieval conditions, while his unconvincing trade-ship argument overlooks land-based caravans, the overland migration of infected rodents, and the many other animals that carry plague.
The passage suggests that Twigg believes that rats could not have spread the Black Death unless which of the following were true?
关键词Twigg，题目问的是rats不可能spread Black Death，除非发生了以下那个事情,削弱题。Twigg用来支持他自己的观点rats不可能spread Black Death的依据有两个：1.老鼠数量不够 2.trade-ship explaination里面的 船上老鼠的数量也不够。 那么可以从这两点入手，选跟这两点意思相反的就可以
选项B 不是这个两点中的一点，老鼠对病免疫，那老鼠之间就不会传染，就rats不可能spread Black Death，变成支持
选项D primarily infested densely populated areas.不是这个两点中的一点 无关选项
选项E other animals 不是这个两点中的一点 无关选项
"rat population in Europe was both too sparse and insufficiently migratory to have spread plague", sparse只有稀少的意思，没有分散的意思，取非是老鼠的数量更多。选D
Unless＝if not,D 老鼠主要集中在人口密集的地方，不能说明老鼠多
1.这道题先搞清题干，Twigg 在什么情况下会认为rat传播Black Death 2.Twigg employs urban case studies suggesting that the rat population in Europe was both too sparse and insufficiently migratory to have spread plague. 3.取非后，老鼠数量大就会引发plague