Match List - I with List - II and choose the correct answer.

List - I	List - II
(a) Metamerism	(i) Coelenterata
(b) Canal system	(ii) Ctenophora
(c) Comb plates	(iii) Annelida
(d) Cnidoblasts	(iv) Porifera

The correct option is a - (iii) b - (iv) c - (ii) d - (i).

To find the correct match, we can analyze the biological characteristics listed in List - I and pair them with the corresponding animal groups in List - II:

(a) Metamerism: Metamerism refers to true segmentation where the body is externally and internally divided into repetitive segments (metameres) with a serial repetition of at least some organs. This feature is a key characteristic of the phylum Annelida (e.g., earthworms).
Therefore, (a) matches with (iii).

(b) Canal system: The water canal system is a unique diagnostic feature found in members of the phylum Porifera (sponges). Water enters through minute pores called ostia into the central spongocoel cavity and exits through the osculum, aiding in nutrition, respiration, and excretion.
Therefore, (b) matches with (iv).

(c) Comb plates: Comb plates are structures consisting of fused cilia that are used for locomotion. They are a defining feature of the phylum Ctenophora (comb jellies), which typically possess eight external rows of these ciliated comb plates.
Therefore, (c) matches with (ii).

(d) Cnidoblasts: Cnidoblasts (stinging cells containing nematocysts) are specialized cells used for prey capture, defense, and anchorage. These cells are characteristic of the phylum Coelenterata (also known as Cnidaria).
Therefore, (d) matches with (i).

By putting all the individual matches together, we get:
a - (iii)
b - (iv)
c - (ii)
d - (i)