Final answer:
An annual external audit by a certified public accountant is the method used to demonstrate financial integrity in missions giving, ensuring credibility and establishing trust through independent verification.
Step-by-step explanation:
The method used to demonstrate financial integrity in missions giving that the question refers to is likely to be the option of an annual external audit by a certified public accountant. This method ensures that an independent entity verifies the financial statements and accounting practices related to missions giving, thereby establishing credibility and trustworthiness. This is a common practice among organizations that seek to maintain transparency in their financial dealings, especially those that receive donations and funds from external sources.
Option b, an annual external audit, serves as a rigorous process that scrutinizes the organization's financial transactions and record-keeping. It is regarded as a high standard of accountability, which can reassure donors and stakeholders that their contributions are being managed appropriately. While other methods, such as internal reports and communication with churches, also support transparency, an audit provides a more formal and systematic assessment of financial integrity.