Consider the following statements about cnidarians: 1 They have tissue level of organization and are diploblastic. 2 Digestion is extracellular and intracellular. 3 Corals secrete calcium carbonate which forms a skeleton. 4 Corals may harbour some photosynthetic dinoflagellates for taking nutrition. 5 They possess a central gastrovascular cavity with a single opening mouth on hypostome.