Regardless of the differences in the approximation of perfect bilingualism, most bilingual communities have one thing in common, that is, a fairly clear functional differentiation of the two languages in respect of speech situations known as ______.

Regardless of the differences in the approximation of perfect bilingualism, most bilingual communities have one thing in common, that is, a fairly clear functional differentiation of the two languages in respect of speech situations known as ______.

A.diglossia

B.bilingualism

C.version

D.domains

正确答案是D