Final answer:
The investigator can conclude that the robber is likely organized and experienced based on the details provided. The correct option is (c).
Step-by-step explanation:
The investigator in this case can conclude that the robber is likely organized and experienced.
Based on the details provided, the robber came prepared with a black ski mask and black clothing, displayed a gun, and handed the clerk a note. These actions suggest that the robber had a plan and knew how to carry out the robbery effectively.
The M.O. (modus operandi) refers to the characteristic method of operation used by a criminal. In this case, the organized and experienced nature of the robbery indicates that the suspect has likely committed similar crimes in the past.