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问题 填空题

（4分）甲烷、乙烷的一氯取代物不存在同分异构体，则碳原子数少于10的烷烃分子中还有哪些烷烃的一氯取代物也不存在同分异构体？请写出这些烷烃的结构简式。（有几种写几种）                                                          

答案

略

单项选择题

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 ply 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.
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单项选择题

不属于化妆品所致皮肤损害的是

A．刺激性接触性皮炎
B．变应性接触性皮炎
C．光变应性接触性皮炎
D．痤疮
E．脂溢性皮炎
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