The correct option is B Anthozoa
Sea anemone is the member of class Anthozoa which includes sessile, marine, polyps, lacking medusa stage. They have gastrovascular cavity divided into chambers to increase the area for digestion. Class hydrozoa includes marine as well as freshwater species that exhibit distinct alternation of polyp and medusa stages. Class Scyphozoa includes marine, free-swimming members with prominent medusa form and reduced or absent polyp stage. Thus, the correct answer is option B.