The diagram illustrates part of the nitrogen cycle. Which processes are P, Q, R and S?
- AP nitrification, Q nitrification, R decomposition, S nitrogen fixation
- BP nitrification, Q nitrogen fixation, R nitrification, S decomposition
- CP nitrogen fixation, Q nitrification, R decomposition, S nitrogen fixation
- DP nitrogen fixation, Q nitrogen fixation, R nitrification, S decomposition