Final answer:
The word 'Chapter' is the most suitable addition to Set P, which includes elements related to written language structure. Correct option is A) Chapter
Step-by-step explanation:
If Set P = {words, phrases, sentence, paragraph}, then the most suitable word which belongs to set P is Chapter. The set contains elements that are all components of written language, specifically those that contribute to text structure. A chapter is a logical extension of this set as it is a larger section of a book or document that encompasses paragraphs, sentences, phrases, and words. Options B) Number, C) Verb, and D) Tense don't fit as well because they are either parts of speech (verb, tense) or unrelated (number) to the structure of text in the way that words, phrases, sentences, or paragraphs are.