Correct Answer:
B. Font Dialog Box
The 'Hidden' checkbox option, which allows users to conceal text in Microsoft Word, is located within the Font Dialog Box. This is because 'Hidden' is considered a character-level formatting attribute, similar to bold, italic, or underline, affecting the display properties of selected text. The Paragraph Dialog Box manages paragraph-level formatting like alignment and line spacing. The Page Setup Dialog Box controls document layout settings such as margins and orientation. The Styles Dialog Box applies predefined sets of formatting, but the direct 'Hidden' attribute is found under Font settings.