Final answer:
The similarities between the nitrogen and phosphorus cycles can be described by option c. Both cycles are driven by microbial activity.
Step-by-step explanation:
The similarities between the nitrogen and phosphorus cycles can be described by option c. Both cycles are driven by microbial activity. In both cycles, microorganisms play a key role in the various processes involved. For example, in the nitrogen cycle, microbial activities such as nitrogen fixation, decay, nitrification, and denitrification are crucial for the cycling of nitrogen through the biosphere.