Which of the following statements regarding the necessary resources to achieve the internal audit plan...

According to the Standards, internal audit activities can be provided through in-house resources, outsourcing, or a co-sourcing model. Therefore, it is possible for all resources to come from outside the organization, but ultimate responsibility and accountability remain with the CAE, management, and the board.

Option A is incorrect because oversight cannot be outsourced. Option B is incorrect—coordination with other assurance providers typically increases efficiency. Option D misstates requirements; co-sourcing is an option, not a mandatory practice.