Final answer:
An Aircraft Maintenance Engineer (AME) requires an Authorized Certification Authority (ACA) endorsement from an Aircraft Maintenance Organization (AMO) to sign a maintenance release.
Step-by-step explanation:
An AME (Aircraft Maintenance Engineer) does not automatically qualify to sign a maintenance release under an AMO (Aircraft Maintenance Organization) unless the AMO grants the person an ACA (Authorized Certification Authority). The correct answer is A. ACA. An AME must have an ACA endorsement to be able to certify the airworthiness of an aircraft or its components after maintenance has been carried out. Without this authorization, the AME does not have the official capacity to release the aircraft back into service.