The correct answer is C. enumeration.
Enumeration is the process of counting or listing things. In the context of the question, the final electoral rolls have been intensively revised through house to house enumeration. This means that each house has been visited and the names of all eligible voters have been recorded.
The other options are incorrect because they do not accurately describe the process of enumeration. Investigation is the process of examining something carefully in order to find out the truth. Enunciation is the act of saying something clearly and distinctly. Documentation is the process of providing written or other evidence to support a claim. Categorization is the process of sorting things into groups based on shared characteristics.
I hope this helps! Let me know if you have any other questions.