A. In the sentence "She quickly reads a book," POS tagging assigns tags like "PRON" (pronoun) to "She," "ADV" (adverb) to "quickly," "VERB" to "reads," "DET" (determiner) to "a," and "NOUN" to "book." This tagging clarifies the roles and grammatical functions of words, aiding syntactic and semantic analysis in natural language processing tasks.