Which one of the following is a true fish according to the biological system of classification, even though several of the names listed contain the word “fish”?

Introduction / Context:
Many animals have common names that include the word “fish”, but not all of them are true fishes in biological classification. Some are insects, some are molluscs, and some belong to entirely different groups. This question tests whether you can distinguish between misleading common names and actual fishes according to zoological criteria. You must identify which one in the list is a true fish.

Given Data / Assumptions:

• The names given are Silverfish, Jellyfish, Cuttlefish, and Flying fish.
• We must decide which one is a true fish as per biological classification.
• True fishes are aquatic vertebrates with gills, fins, and belonging to phylum Chordata.
• We assume standard textbook definitions of fish and other groups.

Concept / Approach:
Silverfish is actually a small, wingless insect found in homes, not a fish. Jellyfish are marine invertebrates belonging to phylum Cnidaria, with gelatinous bodies and tentacles, not vertebrate fishes. Cuttlefish are molluscs related to squids and octopuses, belonging to phylum Mollusca. Flying fish, despite its name, is a true fish that can glide above water using enlarged fins but still fits all criteria of a fish: it lives in water, has gills, and has a typical fish body structure. Therefore, Flying fish is the only true fish in the list.

Step-by-Step Solution:
Step 1: Recall that a true fish must be a vertebrate, have gills, and live in water permanently. Step 2: Examine Silverfish, which lives on land, in bookshelves and damp corners, and is an insect, not an aquatic vertebrate. Step 3: Examine Jellyfish, which are soft bodied marine creatures with radial symmetry and no backbone; they are cnidarians, not fishes. Step 4: Examine Cuttlefish, which are cephalopod molluscs with tentacles and an internal shell; again, not vertebrate fishes. Step 5: Examine Flying fish, which is a marine fish capable of gliding; it has gills, fins, and a vertebrate skeleton, so it is a true fish. Hence, choose Flying fish as the correct option.

Verification / Alternative check:
To verify, think about where each animal is placed in biology textbooks. Silverfish is always shown in chapters on insects and household pests. Jellyfish appear in sections on coelenterates or cnidarians. Cuttlefish is grouped with squids and octopuses in the molluscs chapter. Flying fish, however, appears in the section on fishes, with pictures showing it gliding above the sea while still clearly a bony fish. The consistent classification of flying fish as a genuine fish confirms it as the correct answer.

Why Other Options Are Wrong:
Silverfish is wrong because it is an insect, not an aquatic vertebrate. Jellyfish is incorrect because it is a cnidarian with no backbone and no fish like skeleton. Cuttlefish is also wrong, belonging to the molluscs and having tentacles and a different body plan. Although the word fish appears in all these names, biological classification clearly places them outside the true fishes, leaving only flying fish as the valid choice.

Common Pitfalls:
A common pitfall is to rely on the common name alone and assume that anything ending in “fish” must be a fish. Another mistake is to be unfamiliar with silverfish and think it might be some small aquatic species. To avoid such errors, remember a few classic examples of misleading names: silverfish (insect), jellyfish (cnidarian), starfish (echinoderm), and cuttlefish (mollusc). In contrast, flying fish, swordfish, and catfish are true fishes. Recognising these examples makes such questions easier to handle.

Final Answer:
The correct option is Flying fish, which is a true fish in biological classification, whereas silverfish, jellyfish, and cuttlefish are not fishes despite their names.