Which two elements are commonly involved in nutrient recycling?

The correct choice is the pair of carbon and nitrogen, which are indeed central to nutrient recycling processes in ecosystems. Carbon is fundamental because it forms the backbone of all organic molecules, being a key component of carbohydrates, proteins, lipids, and nucleic acids. Through processes like photosynthesis, organisms such as plants capture carbon dioxide from the atmosphere, converting it into organic carbon compounds. When these organisms die or are consumed by other organisms, the carbon is returned to the soil and atmosphere, thus completing the cycle.

Nitrogen plays a similarly crucial role. It is essential for the production of amino acids, which are the building blocks of proteins, as well as nucleic acids like DNA and RNA. The nitrogen cycle, which includes processes like nitrogen fixation, nitrification, and denitrification, ensures that nitrogen is converted into various forms that can be used by different organisms, effectively recycling it within the ecosystem.

In combination, carbon and nitrogen are involved in key ecological processes such as decomposition and nutrient cycling, ensuring that essential nutrients are available for plant growth and overall ecosystem function. This highlights their critical roles in sustaining life and maintaining balanced ecosystems.