Adoctor is exploring some tissues with a blunt probe. she notices that the tissue is white and fatty and seems to be concentrated within the spinal cord. she is observing
a. gray matter
b. myelin sheaths

The correct answer is option B, that is, myelin sheaths.

Explanation:

Myelin refers to an insulating layer, or a sheath, which get produced surrounding the nerves, comprising those in the spinal cord and the brain. It is formed of fatty substances and protein. This myelin sheath permits electrical impulses to conduct briskly and effectively between the nerve cells.  

The neuron’s myelin sheath comprises the cells containing fat, which shield the axon from electrical activity. The insulation functions to enhance the rate of conduction of signals. The myelin sheath provides the whitish look to the brain's white matter.  

i am going to guess that it is co2.

i think that is new experiments yield untrustworthy data and should be carefully considered, because you don't know what will happen with the experiments.