- AFore skin
- ✓Testis
- CUrethra
- DBulbourethral gland
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$(a)$ Metagenesis is observed in Helminths.
$(b)$ Echinoderms are triploblastic and coelomate animals.
$(c)$ Round worms have organ-system level of body organization.
$(d)$ Comb plates present in ctenophores help in digestion.
$(e)$ Water vascular system is characteristic of Echinoderms.
Choose the correct answer from the options given below.
($i$) It consists of a network of trachea, that open through $12$ pairs of small holes called spiracles present on the lateral side of the body.
($ii$) Thin branching tubes carry oxygen from the air to all the parts.
($iii$) The opening of the spiracles is regulated by sphincters.
($iv$) Exchange of gases take place at the tracheoles by diffusion.