Since 1975 there has been in the United States a dra-
matic decline in the incidence of traditional childhood
diseases such as measles. This decline has been accom-
panied by an increased incidence of Peterson's disease,
a hitherto rare viral infection, among children. Few
adults, however, have been affected by the disease.
Which of the following, if true, would best help to
explain the increased incidence of Peterson's disease
(A) Hereditary factors determine in part the degree
to which a person is susceptible to the virus
that causes Peterson's disease.
(B) The decrease in traditional childhood diseases
and the accompanying increase in Peterson's
disease have not been found in any other
(C) Children who contract measles develop an
immunity to the virus that causes Peterson's
(D) Persons who did not contract measles in child-
hood might contract measles in adulthood, in
which case the consequences of the disease
would generally be more severe.
(E) Those who have contracted Peterson's disease
are at increased risk of contracting chicken pox.
I got the correct ans (c) by process of elimination.but could someone shed some light on the explanation?