Final answer:
In this case, the correct neuron involved in detecting the cold sensation when Melanie touched the brick is a sensory neuron.
Step-by-step explanation:
In the scenario given, Melanie touched a brick and could feel that it was cold. This indicates the involvement of a sensory neuron. Sensory neurons are specialized to detect stimuli from the environment and transfer that information to the central nervous system. In this case, the sensory neuron would carry the information about the cold sensation to the brain. Therefore, the correct answer is A. Sensory neuron.