I have eaten a burger.

1. A burger has been eaten by me.
2. A burger had been eaten by me.
3. A burger was being eaten by me.
4. A burger is being eaten by me.

Converting present perfect active “I have eaten” to passive requires: object (a burger) becomes subject, auxiliary “has been” (since burger is singular), past participle “eaten,” and optional “by me.” Present perfect passive indicates a completed action with present relevance, focusing on the burger rather than the eater. This transformation is common in formal and academic writing when the doer is less important.