two factor authentication

The Personal Identity Verification (PIV) card is used in non-military government agencies for authentication and identification to gain access to systems, networks, and online resources. These cards, in combination with a personal identification number, meet two-factor requirements. PIV credentials also are designed to help reduce counterfeiting and are tamper-resistant.An authenticator app, such as Google Authenticator, is another method to achieve two-factor authentication. It is a free app available for installation on mobile devices.The U.S. federal government authorizes the use of PIVs as well as authenticator apps, depending on the circumstances.Answer the following question(s):

1. In what type of situation would an authenticator app provide adequate two-factor authentication for federal government use? Provide rationale or a citation for your answer.
2. In what type of situation would a PIV be required for federal government use? Provide rationale or a citation for your answer.