The correct option is D Haversian System
The structural units of a bone are made of Haversian systems These include the Haversian canals, circular lamellae and lacunae (the cavities in the bone) that are filled with bone cells called osteocytes.
Bidder's canal is present inside kidney of frog.
Volkmann's canals are the small channels in the bone that communicate with the Haversian canals.
The eustachian tube is a canal that connects the middle ear to the nasopharynx, which consists of the upper throat and the back of the nasal cavity.