What could cause this?

An app builder wants to show Groups as the last navigation menu item in the Salesforce Mobile App.

However, the app builder is not able to select Groups as one of the items on the drop-down menu.

What could cause this?
A . Groups is showing up in the recent section and not in the navigation menu.
B . Groups cannot be the last item in the navigation menu.
C . Groups is included in the Smart Search items but not on the navigation menu.
D . Groups is not included in the selected list for the navigation menu.

Answer: D