Which one of the following is a true fish as per the biological system of classification?

In the biological system of classification, a 'true fish' must belong to the superclass Agnatha, Chondrichthyes, or Osteichthyes, characterized by having a backbone, gills for breathing, and fins [3]. Flying fish (family Exocoetidae) are true bony fishes belonging to the class Actinopterygii (ray-finned fishes). In contrast, other options are 'false' fishes named colloquially. Silverfish are wingless insects of the order Zygentoma [1]. Jellyfish are aquatic invertebrates belonging to the phylum Cnidaria, lacking a backbone and gills [1]. Cuttlefish are marine mollusks of the class Cephalopoda, more closely related to squids and octopuses than to vertebrates. Therefore, only the flying fish meets the taxonomic criteria of a vertebrate fish with a two-chambered heart and gill-based respiration [3].

Sources

1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 9: Indian Biodiversity Diverse Landscape > Fishes > p. 154
2. [3] https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/lepisosteiformes
3. [2] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Oxygen enters the blood in the lungs > p. 92