The answer is, D. Organ system
Glucose is the main provider of energy for the brain and the nervous system. Because the brain is so rich in nerve cells, or neurons, it is the most energy demanding organ, using one half of all the sugar energy in the body. Brain functions such as memory, thinking and learning are closely linked to glucose levels and how efficiently the brain uses this fuel source.
"Phantom Limb Syndrome," the sensation of a body part that is no longer present, but feels like it's still there, is most often due to limbs, after amputation or traumatic destruction. It is due to the cerebral cortex still trying to "make sense of" a limb that used to send signals to it.
When it is painful, it's called "phantom pain" as such.
I have never heard of the four phases of research, but I know that the scientific method can be summarized in four steps.
1. Observe something in nature.
2. Make a hypothesis (prediction) based on that observation.
3. Design and undergo and experiment to test the validity of your hypothesis.
4. Draw a conclusion about your hypothesis based on the results of your experiment.
