The usual composition of a food chain is a producer and multiple consumers.
In a typical food chain, the producer (usually a plant) converts sunlight into energy through photosynthesis, and then consumers (herbivores, carnivores, and omnivores) feed on these producers and each other. Decomposers also play an important role in the ecosystem but are typically not included in the basic structure of a food chain. So, the best answer is "a producer and multiple consumers."