Which file type is primarily used for raw text without formatting?

The correct answer is a text file with the .txt extension, primarily because it is specifically designed to store raw text information without any formatting. This means that a .txt file can hold only plain text characters, which makes it versatile for various applications that require simple text input and output.

Unlike the other file types mentioned, a .txt file does not include additional features like fonts, colors, or layouts, which are common in word processing or presentation files. This simplicity allows .txt files to be easily created, edited, and read by a wide variety of text editors and applications across different operating systems. Additionally, .txt files are lightweight and take up minimal storage space, making them ideal for straightforward text storage needs.

The other options involve formats that are intended for richer content. A Microsoft Word file (.doc) and a Word Open XML document (.docx) are designed for formatted text and include advanced document features like images, tables, and embedded objects. The Portable Document Format (.pdf) is used for documents that need to preserve formatting across different devices and software, intended more for sharing and viewing rather than simple text processing. Hence, the .txt file is the definitive choice for raw text without formatting.