One advantage of fish forming a shoal is:

The correct option indicates that one key advantage of fish forming a shoal is the greater chance of avoiding predators. When fish school together, they create a larger and more dynamic target for predators, making it harder for any one fish to be singled out. This behavior takes advantage of the confusion effect, where the movement of many individuals creates uncertainty for the predator about which fish to attack.

Additionally, shoaling can lead to decreased energy expenditure. Fish moving in a group can reduce the amount of energy needed to swim, as they experience less water resistance and can benefit from the fluid dynamics created by the movements of the fish around them. The coordinated movements of a shoal can optimize their swimming efficiency, allowing them to conserve energy.

While increased competition for food is a potential concern in a shoaling situation, the overall benefits of improved predator avoidance and energy efficiency often outweigh this. Therefore, the advantages of shoaling encompass a combination of factors that enhance survival and efficiency in the marine environment.