单选题 A society's infant mortality rate is an accepted indicator of that society's general health status. Even though in some localities in the United States the rate is higher than in many developing countries, in the United States overall the rate has been steadily declining. This decline does not necessarily indicate, however, that babies in the United States are now, on the average, healthier at birth than they were in the past. Which one of the following reasons, if true, most strongly supports the claim made above about the implications of the decline?

A、 The figure for infant mortality is compiled as an overall rate and thus masks deficiencies in particular localities.
B、 Low birth weight is a contributing factor in more than half of the infant deaths in the United States.
C、 The United States has been developing and has achieved extremely sophisticated technology for saving premature and low-birth-weight babies, most of whom require extended hospital stays.
D、 In eleven states of the United States, the infant mortality rate declined last year.
E、 (E) Babies who do not receive adequate attention from a caregiver fail to thrive and so they gain weight slowly.

【正确答案】 C

【答案解析】[解析] 婴儿死亡率的高低由两个重要因素决定：第一是婴儿出生时的健康状况；第二是婴儿接受的后天护理的好坏，因此若美国在对婴儿，特别是容易死亡的早产以及低出生婴儿护理方面的技术比以前大为提高时，能确保它的婴儿死亡率下降，但并不一定能说明美国现在的婴儿在他们出生时比以前更健康了。由此分析可知，(C)是正确答案，(A)、(B)、(D)和(E)均与本题的答案无关。