【正确答案】It has been observed that in some speech communities, two languages are used side by side with each having a different role to play, and language switching occurs when the situation changes. This constitutes the situation of bilingualism. For these people, the proficiency in the use of two languages is required to fulfill different needs of social communication. A typical example of bilingualism is Canada where both French and English are recognized as official languages.
While the term diglossia, first used by Ferguson in 1959, refers to a sociolinguistic situation similar to bilingualism. But instead of two different languages, ina diglossic situation two varieties of a language exist side by side throughout the community, with each having a definite role to play. One of the most important features of diglossia is the specialization of function of the two varieties. Each variety is the appropriate language for certain situations with very slight overlapping.

【答案解析】[解析] 此题考查的是考生对双语制及高低语的理解。两者都是指存在于同一语言社区的语言现象。双语制是指在同一语言社区同时存在着的两种不同语言，并且这两种语言起着不同的社会作用。使用者可以依需要在两种一语言之间自如地转换。而高低语现象是指在同一语言社区存在着的同一语言的两种变体，这两种变体在该语言社区起着不同的社会作用。同时，高低语现象的一个特征是，两种语言变体分别适用于不同的社会场合，同时也偶有交叉。考生同时还应理解并掌握高低语现象中的high variety与low variety的含义。