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侵蚀性葡萄胎可发生在流产后

绒毛膜癌可发生在葡萄胎之后

绒毛膜癌最早出现的是脑转移

绒毛膜癌最常见的死因是肺转移

前次妊娠为异位妊娠，不发生绒毛膜癌

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服务号

企业号

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维普数据库

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沿着光纤的中轴线直线传播

沿着光纤的外壁多次折射传播

沿着光纤的内壁多次反射传播

沿着光纤螺旋式的曲线传播

Dialects A dialect is a variety of a language spoken by an identifiable subgroup of people. Traditionally, linguists have applied the term dialect to geographically distinct language varieties, but in current usage the term can include speech varieties characteristic of other socially definable groups. Determining whether two speech varieties are dialects of the same language, or whether they have changed enough to be considered distinct languages, has often proved a difficult and controversial decision. Linguists usually cite mutual intelligibility as the major criterion in making this decision. If two speech varieties are not mutually intelligible, then the speech varieties are different languages if they are mutually intelligible but differ systematically from one another, then they are dialects of the same language. There are problems with this definition, however, because many levels of mutual intelligibility exist, and linguists must decide at what level speech varieties should no longer be considered mutually intelligible. This is difficult to establish in practice. Intelligibility(可理解性) has a large psychological component: If a speaker of one speech variety wants to understand a speaker of another speech variety, understanding is more likely than if this were not the case. In addition, chains of speech varieties exist in which adjacent speech varieties are mutually intelligible, but speech varieties farther apart in the chain are not. Furthermore, sociopolitical factors almost inevitably intervene in the process of distinguishing between dialects and languages. Such factors, for example, led to the traditional characterization of Chinese as a single language with a number of mutually unintelligible dialects. Dialects develop primarily as a result of limited communication between different parts of a community that share one language. Under such circumstances, changes that take place in the language of one part of the community do not spread elsewhere. As a result, the speech varieties become more distinct from one another. If contact continues to be limited for a long enough period, sufficient changes will accumulate to make the speech varieties mutually unintelligible. When this occurs, and especially if it is accompanied by the sociopolitical separation of a group of speakers from the larger community, it usually leads to the recognition of separate languages. The different changes that took place in spoken Latin in different parts of the Roman Empire, for example, eventually gave rise to the distinct modem Romance languages, including French, Spanish, Portuguese, Italian, and Romanian. In ordinary usage, the term dialect can also signify a variety of a language that is distinct from what is considered the standard form. of that language. Linguists, however, consider the standard language to be simply one dialect of a language. For example, the dialect of French spoken in Paris became the standard language of France not because of any linguistic features of this dialect but because Paris was the political and cultural centre of the country.

Social Varieties of Language Sociolects(社会方言) are dialects determined by social factors rather than by geography. Socioleets often develop due to social divisions within a society, such as those of socioeconomic class and religion. In New York City, for example, the probability that someone will pronounce the letter when it occurs at the end of a syllable, as in the word fourth, varies with socioeconomic class. The pronunciation of a final in general is associated with members of higher socioeconomic classes. The same is true in England of the pronunciation of h, as in hat. Members of certain social groups often adopt a particular pronunciation as a way of distinguishin A．Y B．N C．NG

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which

what

them

those,

正确

错误