The correct answer is A. Revoke all versions of the signing profile assigned to the developer. AWS Signer allows you to sign your code to ensure its integrity and authenticity. By revoking the signing profile, you ensure that any code signed with that profile is marked as invalid and cannot be deployed. This is the primary method provided by AWS for invalidating code signed by a specific entity or user. This solution directly addresses the requirement to prevent the developer's code from being deployed to the Lambda functions by making the signature provided by that developer unusable.