Answer:
B) a continual input of energy.
Explanation:
An ecosystem can be defined as the natural living habitats of both living and non-living organisms, in which they interact with one another. Essential services such as plant pollination, water purification, nutrient cycling etc that are being provided by the ecosystem are really very vital, important and useful for the sustenance of life, both for humans and enhances social welfare.
An ecosystem is generally considered to be stable if it's capable of applying self-regulating mechanisms in order to return to an equilibrium state, after an experiencing an outside disturbance or perturbation. Thus, a stable ecosystem maintains a natural balance of nutrients and energy.
In an ecosystem, producers are the living organisms that are capable of manufacturing their own food and as such can provide energy or food for the other living organisms (consumers) in a food chain. Thus, producers are mainly known as the foundation of a food chain and are at the top.
Generally, a producer gets energy from the sun and converts it into food. The cells found in producers are capable of converting the energy received directly from the sun into food through a process generally referred to as photosynthesis, converting carbon dioxide from the air, water from the soil, minerals and energy from the sun into organic nutrients.
Hence, a stable ecosystem is characterized by having a continual input of energy.
