Mark the correct answer regarding the given diagram:

• A
  $(a) \rightarrow$ Diploblastic,$(b) \rightarrow$ Triploblastic
• B
  $(a) \rightarrow$ Ctenophora,$(b) \rightarrow$ Annelida
• C
  $(a) \rightarrow$ Coelenterata,$(b) \rightarrow$ Mollusca
• D
  $(a) \rightarrow$ Arthropoda,$(b) \rightarrow$ Hemichordata