Let's discuss each option one by one-
Decomposers- Decomposers are organisms that feed on dead things: dead animal carcasses, dead plant materials and feces. They perform valuable services to keep our earth clean. In recycling of mineral elements within an ecosystem, the responsible direct acting organisms are called decomposers.
Producers- Producers are green plants that can make their own food by using sunlight and inorganic materials. It is a baseline of food chain.
Primary consumer- They are also called as herbivores and they feed on producers.
Secondary consumer- Small carnivores that usually feed on other animals (specially herbivores) are called secondary consumer.
Hence, the right answer is decomposers.