Write the name of phylum.
a) Diploblastic, tissue grade of organisation, symmetrical, polymorphic animals. .
b) Soft bodied, Unsegmented, Bilaterally symmetrical animals with open type circulation.
c) Triploblastic, bilaterally symmetrical, true coelomic animals with metamerism, closed circulation.
d) Triploblastic, chitinous exoskeleton and open parasitic on human beings.

From the following general characters find out corresponding Class with an Example a) Exclusively marine, triploblastic, spines on the skin, radially symmetrical in the adult and bilaterally symmetrical in the larval stage. b) Marine, they migrate towards freshwater for spawning, then their larvae retum to ocean after metamorphosis. c) Triploblastic, bilaterally symmetrical, coelomate and metamerically segmented animals.