In an ecosystem, animals consume to gain energy. If we have, say, a lion that eats a zebra, the lion is eating the zebra to obtain energy. How does the zebra get its energy? Well, the zebra eats producers, or plants, that produce their own food and energy from the sun. Producers are the base of the trophic levels. Many are needed because energy is lost due to metabolic heat in consumers. Producers are essential because they are the foundation for the energy that every single other consumer in the ecosystem will use.
Producers are an essential component of an ecosystem because they create food from inorganic matter for the consumers to eat. Plants like lichens and algae are key producers that convert water, sunlight, and carbon dioxide into carbohydrates. If not for producers, the consumers probably would not have as much or any food to eat!
The answer would be A. carbohydrates (carbs) because carbs are generally composed of sugars and glucose (as an example) has the ratio between carbon, hydrogen and oxygen in a 1:2:1 ratio in its form: C6H12O6