2. 外语
  3. One of medicine’s fundamental beliefs about pregnancy and the development of the human fetus has been challenged. Until recently

One of medicine’s fundamental beliefs about pregnancy and the development of the human fetus has been challenged. Until recently

admin2010-01-15  86
问题      One of medicine’s fundamental beliefs about pregnancy and the development of the human fetus has been challenged. Until recently, it was thought that the fetus was a parasite capable of extracting all the nutrients it needed from the mother. It is now realized that adequate nutrition during the entire course of the pregnancy is necessary for proper fetal development.
     In early pregnancy, certain changes occur in the mother’s gastrointestinal tract, resulting in more efficient absorption of specific nutrients, such as iron and calcium. Furthermore, the maternal blood supply increases, so that nutrients can be transported via the uterine and placental blood systems: If the mother is undernourished, this "lifeline" to the fetus will be inadequately developed. Finally, fat is accumulated within the body to store the energy necessary for lactation (milk production), This preparation for lactation is so important that if the mother is inadequately nourished, it will take place even at the expense of fetal growth. It is a logical developmental occurrence, since in the natural world, no infant can survive without successful breastfeeding, and thus fetal growth is less of a priority.
The passage mainly discusses______
选项 A、how the human fetus develops
B、the benefits of breastfeeding
C、methods of achieving proper maternal nutrition
D、the effect of maternal nutrition on the fetus
答案D
解析 本题询问全文的中心。文章第一段的最后一句就点明了全文的中心，即，怀孕过程中适足的营养对胎儿的正常发育很重要。接下来的文字通过几个不同的时期母亲体内营养状况的变化来说明母亲的营养状况对胎儿的影响。因此，四个选项中只有D击中要害。
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