To choose the correct option, the user needs to understand the purpose and importance of user testing during the development cycle of any software application. User testing is necessary to ensure that the application meets the user's requirements and expectations and identifies any bugs that need to be fixed before release.

Option A is incorrect since selecting the most experienced technical personnel may not provide the necessary feedback for the application's usability and accessibility to non-technical users.

Option B is also incorrect because while the general public may provide a wide range of feedback, they may not be the ideal target audience for the application.

Option C may provide valuable feedback, but it may not be sufficient in identifying issues that may arise with new users.

Option D is the correct answer since users unfamiliar with the application can provide valuable feedback on the application's usability, accessibility, and overall user experience.

Therefore, the correct answer is:

The Answer is: D. Users unfamiliar with the application.