Organisms that synthesize carbohydrates from inorganic compounds using radiant energy are called producers.
Explanation: Producers, like plants, use sunlight to create carbohydrates from carbon dioxide and water through photosynthesis, making them the primary source of organic matter in an ecosystem.
Key points about the other options:
Decomposers: These organisms break down dead organic matter into simpler compounds.
Herbivores: These organisms eat plants.
Carnivores: These organisms eat other animals.