Hello!
The Congolese sentries cut off people's hands because it was proof that they did not waste the supply they had been given (it proved that they were getting their hands cut off when they weren't working).
The correct answer is D. If you take action, and you do not understand what you are doing, you can cause more harm than good.
The Transcontinental Railroad was also instrumental in putting thousands of people to work, and also they were instrumental in transporting cattle and resources in much more efficient ways.