Solution

Cephalopods are marine animals. They are characterized by bilateral symmetry. They have elongated and cylindrical body. They have a distinct head. There are arms or tentacles which are modified and serves as foot in the primitive forms. It is the most active group of mollusca. They are referred as ink fish. They have specialised glands called as ink glands. They have the ability to release ink which helps to escape form the predators. The common examples of the organisms which belong to this group Cephalopods are octopus, squids and nautilus.
Thus, the correct answer is option D.