Which of the following statements are true for phylum Ctenophora?
a.   Cnidoblasts are used for anchorage, defense and for the capture of prey

b.   Digestion is extracellular and intracellular

c.   Polyp and medusa stages alternate with each other during life cycle.

d.   Reproduction takes place only by sexual means.

• A

  (b) and (d)

• B

  (a) and (c)

• C

  (a), (b) and (d)

• D

  (a), (b) and (c)