The correct option is B Hagfish
Osmoconformers are marine animals which in contrast to osmoregulator, maintain osmolarity of their body fluids such that it is always equal to the surrounding seawater. They maintain internal solute concentrations within their bodies at a level equal to the osmolarity of the surrounding medium. Hagfish is a vertebrate. So, None of the options are correct.
Therefore, the correct answer is option D.