Final answer:
To create a custom Excel template, click the File tab, select Save As, click Browse, and change the file type to .xltx. This saves your workbook as a reusable template. So the correct answer is option A.
Step-by-step explanation:
To create a custom template in Excel, follow these instructions: Click the File tab, select Save As, then click Browse, and change the file type to .xltx. This option is specifically for saving templates in Excel.
The file extension .xltx stands for Excel Template, which saves the workbook as a template that you can use to start new workbooks in the future. On the other hand, the .xlsm format is for Excel workbooks that contain macros, and the .xlam format is used for Excel Add-Ins.
Choosing these formats would not be appropriate for creating a standard template. The last option, which involves changing settings in Options, is not a standard or correct method to save a file as a template.