You create a new ribbon button for a model-driven app. But it does not work as you expected. You need to troubleshoot the button functionality. 
What two steps should you take to achieve your goal?

Answer options:

A.Open Ribbon Workbench
B.Open App Checker
C.Add &ribbondebug=true to the app’s URL
D.Check button rule
E.Add &ribbonbench=true to the app’s URL
F.Open Command Checker

Correct Answers: C and F 
Power Apps provides the Command Checker tool that helps you to troubleshoot the ribbon buttons. The tool produces information about button visibility, actions, problems with rules. 
You need to enable the Command Checker by adding the &ribbondebug=true to the app’s URL (Number 1). After that, you click on three vertical dots (Number 2) to open a menu and select the “Command checker” item (Number 3). 

When you create a new command button, you need to address two elements: rule and actions.
The rule defines when button’s state within the application, like enable/disable state of the button when some field is changed or who can see the button. There are two types of rules: enable (should the command button be enabled) and display (should the rule be visible for the users). 
The action describes the button behavior, like what should happen when the button is clicked. There are two types of command button actions that users can define in the OnClick event: execute the custom logic using JavaScript code or open a specific URL. It can be the dynamic URL if the business logic of your app requires it. 
Using the Command checker, you can “drill down” the command bar tree (Number 1) and select the button that you have a problem with (Number 2). On the right side of the Command checker screen, you can select the Command properties of the button (Number 3).This tab presents the button’s Actions, Enable Rules, and Display Rules. You can verify why the button is hidden, like the Display Rule evaluated to false on a page load (Number 4). 

All other options are incorrect. 
For more information about the Command button rules and actions, please visit the below URLs: 

https://powerapps.microsoft.com/en-us/blog/introducing-command-checker-for-model-app-ribbons/
https://docs.microsoft.com/en-us/powerapps/developer/model-driven-apps/define-ribbon-commands
https://docs.microsoft.com/en-us/powerapps/developer/model-driven-apps/define-ribbon-enable-rules
https://docs.microsoft.com/en-us/powerapps/developer/model-driven-apps/define-ribbon-display-rules
https://docs.microsoft.com/en-us/powerapps/developer/model-driven-apps/define-ribbon-actions