Answer:
c. a final walk through should be done preferably with two people retaking samples for the last time.
Explanation:
In a survey, every little detail is essential for solving the case. It is important that all possible samples are connected so that nothing is missed out on.
So one of the last steps, just to make sure that they have everything they need in order to come with a solution and go forward with the investigation, is a final walk through should be done preferably with two people retaking samples for the last time.