9) A

We need to know that neurones that detect a certain stimulus are called sensory neurones.

1 – Sensory neurones are the neurones that detect stimulus first in a reflex action. If sensory neurones are unable to detect a certain stimulus, then there will be no reflex action to the stimulus. So 1 is correct.

2 – If the patient can see that the stimulus is taking place and they know it will cause harm to the body, they can then take appropriate action to stop the application of the stimulus.

3 – The patient would not be able to sense pain as the neurones are unable to sense the pain.

4 – Again, they will not be able to sense the pain.

Only statements 1 and 2 are correct, meaning that option A is correct.