The correct answer is option 4 - Insects. In terms of the number of identified species, insects are the most abundant group.

Option 1 - Fungi: Fungi are a diverse group of organisms, but they have fewer identified species compared to insects. Fungi include organisms like mushrooms, yeasts, and molds.

Option 2 - Green plants: Green plants also have a large number of identified species, but they are less abundant than insects. Green plants include flowering plants, ferns, mosses, and algae.

Option 3 - Bacteria: Bacteria are a highly diverse group of microorganisms, but they have comparatively fewer identified species than insects. Bacteria are found in various habitats and play important roles in ecosystems.

Option 4 - Insects: Insects are incredibly diverse, with over a million identified species. They are found in nearly every habitat on Earth and play essential roles in ecosystems as pollinators, decomposers, and prey for other animals.

In conclusion, while all the options are diverse groups, insects have the highest number of identified species, making them the most abundant group in terms of species.