The correct option is D Sub mandibular gland
The ducts of the salivary glands allow the passage of salivary juice from the glands to the oral cavity:
Parotid duct (Stenson duct): Connects the parotid gland to the buccal mucosa, adjacent to maxillary second molar submandibular duct
(Wharton duct): connects the submandibular gland to the floor of the mouth
Duct of Rivinus: the sublingual gland drains through numerous small ducts all of which open into the floor of the mouth and are collectively termed the duct of Rivinus