Explanation
A permission set containing the salary record type and assigning it to the appropriate users would allow only those users to create salary applicant records, while still allowing all users to view all applicant records. This is the most granular and flexible way to meet the requirement

Explanation
To display the actions on the Lightning record page, two components could be included on the layout:
Highlights panel: The highlights panel displays key information and actions for a record based on the compact layout. Users can see and perform actions such as edit, clone, delete, follow, etc. from the highlights panel. [Source] Activities: The activities component displays tasks and events related to a record. Users can also create new tasks and events, log calls, send emails, and view past activities from this component.

Explanation
The feature that the app builder should use to allow users to create the opportunity is a quick action. A quick action is a type of custom button or link that can create or update records, log calls, send emails, or launch flows from a record page or a global menu. The app builder can create a quick action on the account object that creates an opportunity record with pre-populated fields. Option B is incorrect because a default action is not a valid term, but rather a standard action that appears on every record page by default, such as Edit or Delete. Option C is incorrect because a custom button is not suitable for this requirement, as custom buttons can only display a URL or execute JavaScript when clicked. Option D is incorrect because a custom link is not suitable for this requirement, as custom links can only display a URL or execute JavaScript when clicked.