In Biology, group behavior refers to actions made by one organism that help to the survival of another organism in the group.
Some examples are:
• Meerkats have lookouts for predators
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• Bees have designated individuals for different tasks, such as foraging for food or defending the nest.
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• Sharing food resources.
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• Migrating birds fly in formation to conserve energy.
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• Fish swim in schools to avoid predators
One consequence of the organisms living in groups and doing group behaviors is that is easier to find a mate, given that they don't have to travel to find another individual of the same species.
This means that B) having an easier time finding mates, would be the right answer.