The correct option is C Liver fluke
Bilaterally symmetrical means left and right halves of the body have the same design. Dorsiventrally flattened means the front and back of the organism are flat. These two features are present in the organisms belonging to group Platyhelminthes. Liver fluke is one of the examples of group Platyhelminthes. It possesses both features. Hence, the correct answer is option A.