What is common in Amoeba, Starfish, Ant and Spider ?

Correct option is A

The correct answer is They all lack back bone.
Amoeba, Starfish, Ant, and Spider all lack a backbone, making them invertebrates. Invertebrates are a diverse group of animals that do not possess a vertebral column. Amoeba is a unicellular organism without any defined structure like a backbone. Starfish, belonging to the echinoderms, also do not have a backbone. Ants and spiders, which are arthropods (insects and arachnids, respectively), also lack a backbone. The other options are incorrect because not all of these creatures have scales, lay eggs, or live in water.