【单选题】Increasingly, historians are blaming diseases imported from the Old World for the great disparity between the native population of America in 1492—new estimates of which jump as high as 100 million, o...
A.
recur more frequently than chronic diseases.
B.
involve populations with no prior exposure to a disease.
C.
usually involve a number of interacting diseases.
D.
are less responsive to medical treatment than are other diseases.