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The scenario in the question stem describes a reflex arc. During a reflex arc, sensory receptors detect pain and a signal is sent via a sensory neuron to the spinal cord. There, the afferent signal moves to an interneuron where it is processed resulting in an efferent signal being sent to the motor neuron, after which the reflexive action (pulling away the hand) occurs. (B) is the correct answer.

Expert Approach:
A quick peek at the answer choices here reveals that they have a lot in common. In fact, every one of them begins with a sensory neuron and ends with a motor neuron, which tells me two important things: First, that I don?t have to evaluate the truth of those parts of the answer choices, and second, that whatever sequence the question is talking about must begin with a sensory neuron and end with a motor neuron. In fact, the scenario in the stem involves a pain reflex arc?one of the body's automatic, super-fast responses to things like touching a hot stove. I know that the pathway of this arc involves three main components: the sensory neuron (responds to the heat), the interneuron (acts as a messenger in the spinal cord), and the motor neuron (makes the muscles move the hand), and I see that sequence reflected in (B).I also know that the reason reflex arcs are so fast is that they bypass the brain, happening entirely within the periphery and the spinal cord; this ensures the quickest possible response to danger. This fact alone would allow me to find the correct answer here, as (B) is the only option that doesn?t include a neuron in the brain. Even if I had been unsure as to whether reflex arcs can pass through the brain or not, I could at least have eliminated (A) and (D), on the basis of the fact that a sensory neuron wouldn?t bypass the thalamus and project directly to cortex?especially motor cortex.

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