If plants were removed from an area, which statement below

describes best the outcome?

Well, I can't see which statements you can choose from but here's what would happen: If all species of plants were to be removed form an area, oxygen levels would decrease, given that trees are plants and provide oxygen for living beings. All animals, not just herbivores, would start dying because thye have no food. This is because primary consumers, like rabbits and bugs, eat the plants. Those rabbits and bugs are food for secondary consumers, such as snakes and minks. Those snakes and minks are food for tertiary consumers and so on and so forth.

Summary: If plants were to disappear, all life in that area would cease to exsist.