[单项选择] Americans Decrease Increasingly, historians are blaming diseases imported from the Old World for the staggering disparity(不同) between the indigenous (本土的) population of America in 1492—new estimates of which soar as high as 100 million, or approximately 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 precipitous(险峻的) decline, and it is highly probable that the greatest killer was epidemic disease, especially as manifested in virgin-soil (处女地) epidemics. Virgin-soil epidemics are those in which the populations at risk have had no previous contact with the diseases that strike them and are therefore immunologically(免疫学的) almost defenseless. That virgin-soil epidemics were important in American history is strongly indicated by evidence that a number of dangerous maladies(病)—small pox, measles(
A. refute a common misconception
B. provide support for hypothesis
C. analyze an argument
D. suggest a solution to a dilemma