The correct option is A Food chain and decomposers
An ecosystem includes different communities of plants, animals and microbes together with their physicochemical environments.
It consists of two major components, biotic or living components and nonbiotic or nonliving components.
Biotic components include plants, animals, decomposers. Nonliving components include air, water, land.
A food chain is a chain in an ecosystem where there is transfer of food and energy from one organism to another in a sequence.
Decomposers like fungi and bacteria from the food chain. Decaying plants produces organic wastes into inorganic materials. Such as nutrient-rich soil etc. Decomposers complete the life cycle and return the nutrients to the soil. Sometimes, it may return to the oceans for use by autotrophs.
Thus, the correct answer is 'Food chain and decomposers.'