C. Their camera
Toolmarks are the impressions left by an object or tool on it's contact surface. Toolmarks are searched and collected in a crime scene to relate a link with the tool which has created them. In crime scene investigation, toolmarks found in the scene of crime should be photographed by the analyst in close range, mid range and overview range shots in order to record it's original location, shape, size and number if multiple tool marks are present.
The forensic scientists at the crime scene or investigators need to take a picture before anything or anyone starts messing with the scene. Taking the pictures will help solve the case. If you start trying to make a cast then it might mess with the evidence. You always need to take pictures of everything so if you make a cast then you won't be able to take an original picture of the evidence.