As part of their quoting and ordering process, a company needs to send POFs to their document storage system's REST endpoint that supports OAuth 2.0. Each Salesforce user must be individually authenticated with the document storage system to send the PDF.
What is the optimal way for a developer to implement the authentication to the REST endpoint?

A developer wrote a class named asccuntRisteryManager that relies on field history tracking. The class has a static method called getaccountHistory that Lakes in an Account as a parameter and returns a list of associated accountHistory object records.
The following test fails:

What should be done to make this test pass?

Universal Containers develops a Salesforce application that requires frequent interaction with an external REST API.
To avoid duplicating code and improve maintainability, how should they implement the APL integration for code reuse?

A developer is trying to decide between creating a Visualforce component or a Lightning component for a custom screen.
Which functionality consideration impacts the final decision?

The head of recruiting at Universal Containers (UC) wants to provide all internal users the ability to search for open positions by role, department, and location via a new recruiting app. In addition to search, users of the app should be able to refer a friend, apply for a position, and review the status of their current submissions.
The app will be surfaced to UC's existing iOS and Android users via the standard mobile app that Salesforce provides. It has a custom user interface design and offline access is not required.
Given these requirements, what is the recommended approach to develop the app?