The figure shows the pathway of a reflex action in a person who has touched a sharp pin.
Figure: The pathway of a reflex action from the skin of a finger to a muscle in the arm

Name the neurones labelled A, B and C in the figure.
Name the junction labelled X.
Give one reason why a reflex action is faster than a voluntary response.
4 exam-style questions on AQA GCSE Biology 5.2.1 Structure and function. Each one has a worked solution and a mark scheme showing where the marks go.