What should you add to the add-in

You are developing a new Microsoft Office Add-in to integrate a corporate invoicing system and Microsoft Excel.
You need to add a new button to the Office ribbon.
What should you add to the add-in
A. a task pane
B. a dialog
C. a custom function
D. a command

Correct Answer: D
Explanation/Reference:
Explanation:
Add commands to a custom group
1. In the Customize the Ribbon window under the Customize the Ribbon list, click the custom group that you want to add a command to.
2. In the Choose commands from list, click the list you want to add commands from, for example, Popular Commands or All Commands.

3. Click a command in the list that you choose.
4. Click Add.
5. To see and save your changes, click OK.
Reference: https://support.office.com/en-us/article/customize-the-ribbon-in-office-00f24ca7-6021-48d3-9514-a31a460ecb31