Final answer:
In Microsoft Excel, the default worksheet names are Sheet1, Sheet2, etc., beginning with the number 1 and increasing sequentially for additional sheets.
Step-by-step explanation:
The default names of worksheets in Microsoft Excel are Sheet1, Sheet2, etc. When you open a new workbook in Excel, it typically starts with three worksheets, and the default naming convention is to simply append a numeric value starting with 1 to the word 'Sheet.' This makes the first worksheet Sheet1, followed by Sheet2 for the second, and so on. This convention helps in organizing and identifying worksheets within a workbook.