To solve this problem, we need to analyze each statement and determine which ones are correct:$\newline \bullet$(a) Metagenesis is observed in Helminths.$\newline$ - Metagenesis refers to the alternation of generations between sexual and asexual phases.$\newline$ - This is typically observed in some cnidarians, like jellyfish, not in helminths (parasitic worms).$\newline$ - Therefore, this statement is incorrect.$\newline \bullet$(b) Echinoderms are triploblastic and coelomate animals.$\newline$ - Echinoderms, such as starfish and sea urchins, are indeed triploblastic, meaning they have three germ layers.$\newline$ - They are also coelomate, having a true coelom.$\newline$ - Therefore, this statement is correct.$\newline \bullet$(c) Round worms have organ-system level of body organization.$\newline$ - Roundworms, or nematodes, exhibit an organ-system level of organization.$\newline$ - This means they have specialized organs and systems for different functions.$\newline$ - Therefore, this statement is correct.$\newline \bullet$(d) Comb plates present in ctenophores help in digestion.$\newline$ - Comb plates, or ctenes, in ctenophores are used for locomotion, not digestion.$\newline$ - Therefore, this statement is incorrect.$\newline \bullet$(e) Water vascular system is characteristic of Echinoderms.$\newline$ - The water vascular system is a unique feature of echinoderms, used for locomotion, feeding, and respiration.$\newline$ - Therefore, this statement is correct.$\newline$Based on the analysis, the correct statements are:$\newline \bullet$(b) Echinoderms are triploblastic and coelomate animals.$\newline \bullet$(c) Round worms have organ-system level of body organization.$\newline \bullet$(e) Water vascular system is characteristic of Echinoderms.$\newline$This corresponds to Option 4: (b), (c) and (e) are correct.