Abolish slavery was the reform that a commission insisted must happen in Puerto Rico before any other reforms were made.
On March 22, 1873, slavery was "abolished" in Puerto Rico, but with one significant caveat. The slaves were not emancipated; they had to buy their own freedom, at whatever price was set by their previous owners. The law required that the former slaves work for another three years for their former masters, other people interested in their services, or for the "state" in order to pay for some compensation
The correct answer between all the choices given is the third choice or letter C. I am hoping that this answer has satisfied your query and it will be able to help you in your endeavor, and if you would like, feel free to ask another question.