The animals having a blood-filled coelomic cavity belong to which phylum?

Identify and write the names of the parts labeled as $A, B, C$ and $D$ in the given figure of a seahorse in your answer book.

State reasons for the following:
$(a)$ Mammals have mammary glands.
$(b)$ Annelids have a true body cavity.
$(c)$ Fish possess gills.

Give the points of differences between non-chordates and chordates.

You are given leech,Nereis,Scolopendra,prawn,and scorpion; all have a segmented body organization. Will you classify them in one group? If no,give the important characters based on which you will separate these organisms into different groups.

Sehai and Sidak observed an animal in their garden. Sehai called it an insect while Sidak said it was an earthworm. Choose the character from the following which confirms that it is an insect.