請依下文回答第 11 題至第 13 題
There is no single cause of mental retardation, but researchers have uncovered several causes, some of which are
preventable. Brain damage due to genetic conditions is a well-known cause of mental retardation. Most people are
familiar with Down’s syndrome, which is caused by the formation of an additional chromosome. The normal number
of chromosomes for people is 46; babies with Down’s syndrome have 47. Another chromosome-related cause of
mental retardation is a malformation of the X-chromosome. Fortunately, blood tests can detect this problem early and
immediate measures can be taken to limit the damage.
Not all brain damage resulting in mental retardation occurs because of problems in the genetic makeup of the
infant. Certain infectious diseases that the mother may contract during pregnancy can adversely affect the developing
brain of the baby, particularly if the mother catches these diseases during the first three months of her pregnancy.
These diseases include rubella, herpes simplex, and syphilis. Because they are infectious, to a certain extent they are
preventable. Another preventable cause of mental retardation in newborns relates to what the pregnant woman ingests.
Certain drugs are known to hinder the development of the baby’s brain such as thalidomide. However, the most easily
preventable cause of mental retardation is fetal alcohol syndrome. Drinking as little as one or two glasses of wine a
week during pregnancy could result in physical and intellectual impairments in the infant. 【題組】12 According to the passage, which of the following is an infectious disease?
(A) Thalidomide (B) Syphilis
(C) Fetal alcohol syndrome (D) Down’s syndrome
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