Question

Study the following and pick up the correct combinations:

• A. II, III
• B. I, IV
• C. I, II
• D. III, IV

Hint:

{Cnidarian Classes:}

• {Hydrozoa:} Polyp & Medusa ({Obelia}).
• {Scyphozoa:} Medusa dominant ({Aurelia}).
• {Anthozoa:} Polyp only ({Adamsia}).

Answer 1

The Correct Option is B

Step 1: Evaluate Each Row:

I. Scyphozoa (Jellyfish): The medusa stage is dominant. The polyp stage is reduced or absent in the life cycle. \textit{Aurelia} is a classic example. The description "Only medusoid zooids" is acceptable in the context of general classification contrasts (vs Anthozoa). (Correct)
II. Anthozoa (Sea Anemones/Corals): They exist only in the Polyp form. They do not have a Medusa stage. \textit{Adamsia} is a Sea Anemone. The feature "Polyp and Medusa" is wrong. (Incorrect)
III. Hydrozoa: They typically exhibit alternation of generations (Metagenesis) with both Polyp and Medusa stages (e.g., \textit{Obelia}). Some are only polyps (\textit{Hydra}), but the example given is \textit{Obelia}, which has both. The feature "Only polypoid" is incorrect for the group/example pair. (Incorrect)
IV. Hirudinea (Leeches): These annelids have anterior and posterior suckers for attachment and locomotion. \textit{Pontobdella} is a marine leech. (Correct)

Step 2: Conclusion:
Combinations I and IV are correct.