Exocoetus is a genus of flying fishes. It is a bony fish. The body is covered with cycloid scales. The mouth is wide, and the jaws bear teeth. It is a marine fish. The tail has hypobatic fins as the ventral lobe.

Flying fish (Exocoetus) is the correct answer to the given question. Flying fish are a unique group of fish that have the ability to glide or "fly" above the water surface using their specialized pectoral fins. They are known for their impressive flying abilities, which allow them to cover significant distances and evade predators.

Below is a detailed explanation of why option 'D' (Exocoetus) is the correct answer.

Flying Fish - Exocoetus:
Flying fish belong to the genus Exocoetus, which is a type of marine fish found in warm and tropical waters around the world. There are around 64 species of flying fish known to exist. They are characterized by their long, slender bodies, large pectoral fins, and a deeply forked tail. These adaptations enable them to propel themselves out of the water and glide for considerable distances.

Specialized Pectoral Fins:
The pectoral fins of flying fish are their main adaptation for gliding. These fins are elongated and have a wing-like shape, allowing them to act as wings when the fish leaps out of the water. The enlarged surface area of the pectoral fins, combined with their streamlined body shape, helps generate lift and keep the fish airborne.

Gliding Abilities:
When a flying fish encounters a threat or disturbance in the water, it can rapidly accelerate and launch itself into the air. It achieves this by beating its tail against the water surface, which propels it forward and upward. Once airborne, the fish spreads its pectoral fins and adjusts their angle to maintain balance and control its flight. By continuously beating its tail and adjusting the position of its fins, the flying fish can glide for distances of up to 200 meters at speeds of around 70 km/h.

Benefits of Flying Abilities:
The ability to fly above the water surface provides several advantages to flying fish. Firstly, it allows them to escape from predators such as larger fish or marine mammals. Secondly, it helps them cover more distance in search of food or suitable habitats. Additionally, by spending less time in the water, flying fish can reduce their exposure to certain parasites or predators that exist in the marine environment.

In conclusion, flying fish (Exocoetus) is the correct answer to the given question. These remarkable fish have evolved specialized pectoral fins that enable them to glide or "fly" above the water surface. Their flying abilities provide them with advantages such as escaping predators and covering more distance in search of food or suitable habitats.