How should internal audit function maintain its independence?

Group of answer choices

Have independent external auditors perform assurance and attestation service, and internal auditors provide consulting and advisory services.

Internal audit function should work with independent external auditors to collaborate their audit together.

Internal audit function cannot achieve independence because it is an integrated part of the business, however, the auditors should try their best to be objective while providing services.

By positioning the function parallel to the executive management and have the function report directly to the board.