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　Increasingly, historians are blaming diseases imported from the Old World for the staggering disparity between the indigenous population of America in 1492-new esti- mates of which soar as high as 100 million, or approxi- (5) mately one-sixth of the human race at that time-and the few million full-blooded Native Americans alive at the end of the nineteenth century. There is no doubt that chronic disease was an important factor in the precipi- tous decline, and it is highly probable that the greatest (10) killer was epidemic disease, especially as manifested in virgin-soil epidemics.

　　Virgin-soil epidemics are those in which the popula- tions at risk have had no previous contact with the diseases that strike them and are therefore immunologi- (15) cally almost defenseless. That virgin-soil epidemics were important in American history is strongly indicated by evidence that a number of dangerous maladies-small- pox, measles, malaria, yellow fever, and undoubtedly several more-were unknown in the pre-Columbian (20) New World. The effects of their sudden introduction are demonstrated in the early chronicles of America, which contain reports of horrendous epidemics and steep population declines, confirmed in many cases by recent quantitative analyses of Spanish tribute records and (25) other sources. The evidence provided by the documents of British and French colonies is not as definitive because the conquerors of those areas did not establish permanent settlements and begin to keep continuous records until the seventeenth century, by which time the (30) worst epidemics had probably already taken place. Furthermore, the British tended to drive the native populations away, rather than enslaving them as the Spaniards did, so that the epidemics of British America occurred beyond the range of colonists' direct (35) observation.

　　1. The primary purpose of the passage is to

　　(A) refute a common misconception

　　(B) provide support for a hypothesis

　　(C) analyze an argument

　　(D) suggest a solution to a dilemma

　　(E) reconcile opposing viewpoints

　　2. According to the passage, virgin-soil epidemics can be distinguished from other catastrophic outbreaks of disease in that virgin-soil epidemics

　　(A) recur more frequently than other chronic diseases

　　(B) affect a minimum of one-half of a given population

　　(C) involve populations with no prior exposure to a disease

　　(D) usually involve a number of interacting diseases

　　(E) are less responsive to medical treatment than are other diseases

　　3. According to the passage, the British colonists wereunlike the Spanish colonists in that the British colonists

　　(A) collected tribute from the native population

　　(B) kept records from a very early date

　　(C) drove Native Americans off the land

　　(D) were unable to provide medical care against epidemic disease

　　(E) enslaved the native populations in America