Quick Parts in Word is about reusing content you’ve created. It lets you store blocks of text, graphics, or fields that you can insert quickly into any document, making your workflow faster and consistent. A common use is inserting Document Property data—metadata such as the document’s author, company, title, or last modified date—so you can pull that information into multiple documents without typing it each time. This is why this option is the best answer: it describes the purpose of Quick Parts as a way to insert built-in content like Document Property data. Quick Parts isn’t used for changing page color schemes (that’s the Page Color option under Design), it isn’t for spell checking (that feature is in Spelling under Review), and it isn’t for inserting pictures (that’s found under Insert > Pictures).