The diagram illustrates a simple reflex arc. What are the names of the structures labelled P, Q and R?
- AP: motor neurone, Q: relay neurone, R: sensory neurone
- BP: motor neurone, Q: sensory neurone, R: relay neurone
- CP: sensory neurone, Q: motor neurone, R: relay neurone
- DP: sensory neurone, Q: relay neurone, R: motor neurone