What is the default file-extension of Notepad on Windows?

Notepad is a basic text editor included with Microsoft Windows, designed for creating and editing plain text files. Its default file extension is .txt (C), which signifies a plain text document without any special formatting or embedded objects.

• .docx (A) is the file extension for Microsoft Word documents, which support rich text formatting and various document features.
• .html (B) is used for HyperText Markup Language files, which are web pages, though Notepad can be used to edit them.
• .xlsx (D) is the file extension for Microsoft Excel spreadsheets, used for tabular data and calculations.