Lilustrte the recursiveness of phrase structure rules with examples.
The recursiveness of phrase structure rules refers to the properties due to which the phrase structure rules can generate an infinite number of sentences, and sentences with infinite length For example, an S contains a VP that may contain another S； an VP may include an S that contains another VP; a PP consists of an NP that may be followed by another PP； and an NI may take a PP that includes an NP ardor an S.
评分标准：要点答对得7分，举出例子给3分；答错、没有答全或没有举例，酌情扣分
