单项选择题 As modern linguistics aims to describe and analyze the language people actually use, and not to lay down rules for “correct” linguistic behavior, it is said to be _____.？

单项选择题 需要计算征收城建税、教育费附加和地方教育附加的税种有（）

单项选择题 Of the following sound combinations, only _______ is permissible according to the sequential rules in English.（ ）