Question

Which of the following animals is a fish?
A)Shark
B)Star fish
C)Silverfish
D)Jellyfish

Answer 1

In several areas of medical and biological research, fish are important laboratory animals. For example, the readiness of many fish to acclimate to captivity has allowed biologists to study behaviour, physiology and even ecology under relatively natural conditions.

Complete answer:
Starfish are echinoderms (spiny skinned sea urchins). They are also known as sea stars, and despite the name given to them, they are not really fish. Starfish cannot swim and do not use gills to breathe. Starfish are present in the deep blue sea of the ocean and shallow waters. They're present in every ocean in the world. They're never found in freshwater.
Silverfish are tiny inch-long insects that get their name from their grey metallic glow, their tapered body, and their swimming movements while they're moving. They're appropriately named because they look like little fish but they are not real fish. These bugs seem to have two long antennae in the front with two eyes and three cerci and filaments at the end of their abdomen.

Jellyfish has been around for millions of years, long before dinosaurs lived on Earth. Pulsing along our ocean currents, these jelly-like animals can be found in both cold and warm seas, deep and shallow, and along the coasts. Some jellyfish are clear, while others are vivid colours of pink, yellow, blue and purple. The confusion between fish and jellyfish is possibly due to the name they share as well as the fact that they all live in water.
Sharks are a species of fish that has no bones, just cartilage. Some portions of their skeleton, such as their vertebrae, are calcified. Cartilage, a strong fibrous substance, is softer than bone, and our nose and ears are made of cartilage.Sharks belong to the group of fish called Elasmobranchii, which also includes sharks, skates and ratfish. Elasmobranchii are all fish that have no bone, only cartilage.

Hence, the correct answer is option (A)

Note: Most sharks can see well in dark light areas, have a great night vision, and can see colours. The back of shark eyeballs has a reflective layer of tissue called a tapetum. This allows sharks to see exceptionally well with little light.