At an Arson Scene, Collecting a Substrate Control Would Require

At an arson scene, collecting a substrate control would require the arson investigator to:

A) Collect a sample from the center of a potential accelerant stain.
B) Collect samples of surface material from areas far away from the fire's origin.
C) Collect a piece of the surface material near the fire's origin that he or she believes was not exposed to the accelerant.
D) Collect a sample of the vapors at the fire origin.