Comprehensive and Detailed Step-by-Step
Understanding Application Scope and Picker:
The Application Picker in ServiceNow allows developers to switch between different applications (scopes).
When you select an application from the Application Picker, the Application Scope is set to that application, enabling you to develop or configure within that scope.
Why Other Options Are Incorrect:
Option A: The Global application does appear in the Application Picker.
Option B: Selecting Global does not set the scope to Incident; it sets the scope to the Global application, which is not restricted by scoped boundaries.
Option D: Selecting an application does indeed set the Application Scope.
Reference:
ServiceNow Developer Documentation on Application Scope.

Explanation/Reference: https://community.servicenow.com/community?
id=community_question&sys_id=8af90f29db5cdbc01dcaf3231f96197c