Trophic levels are formed by -

The correct answer is Option 4

Key Points​​Trophic level:

• Trophic level, step in a nutritive series, or food chain, of an ecosystem.
• The organisms of a chain are classified into these levels on the basis of their feeding behaviour.
• The first and lowest level contains the producers, green plants.
• The plants or their products are consumed by the second-level organisms—the herbivores, or plant eaters.
• At the third level, primary carnivores, or meat eaters, eat the herbivores; and at the fourth level, secondary carnivores eat the primary carnivores.
• These categories are not strictly defined, as many organisms feed on several trophic levels; for example, some carnivores also consume plant materials or carrion and are called omnivores, and some herbivores occasionally consume animal matter.
• A separate trophic level, the decomposers or transformers, consists of organisms such as bacteria and fungi that break down dead organisms and waste materials into nutrients usable by the producers.