Final answer:
The authority to approve Navy and Marine Corps Commendation Medals falls to officers within the chain of command, typically of a certain rank or position, but specific grades or positions are not provided in the information given.
Step-by-step explanation:
The approval authority for the Navy and Marine Corps Commendation Medal and below for all ranks up to O-6 (Captain/Colonel) falls to officers who have been granted the necessary authority in the chain of command. However, the provided information does not include specific details regarding which officers or grades have this approving capability. In order to give approval for the commendation medals, the officer typically should hold a certain position that comes with this responsibility, which could vary based on the branch of service and specific circumstances. For definitive guidance on this topic, one must refer to the current military regulations or directives that govern service awards.