Final answer:
The correct answer is option c. Decomposition is the process that breaks down dead material into simple compounds for natural recycling, including conversion within the nitrogen cycle through steps like nitrogen fixation, ammonification, nitrification, and denitrification.
Step-by-step explanation:
The breakdown of dead matter and waste into simple compounds that are directed back into the natural cycle of living things is called decomposition. This process is essential for recycling nutrients, including nitrogen, which is a key component for many biological processes. The nitrogen cycle involves several steps to convert nitrogen into various forms that can be used by living organisms.
One of these steps is nitrogen fixation, where nitrogen gas (N₂) is converted into ammonia (NH₃), which plants can easily use. Other steps include ammonification, where organic nitrogen is turned into ammonium (NH₄+); nitrification, where ammonium is converted into nitrites (NO₂-) and then nitrates (NO₃-); and denitrification, which converts nitrates back into nitrogen gas (N₂), completing the cycle.