Answer:
The correct answers are: "relevant", "reliable", and "easy to find".
Explanation:
Although "extensive" research is an interesting type of quality information, it is not mandatory and there are a lot of short researches which do their part very well. That is the same for "copyrighted" because it is only interesting for confidence, although not mandatory for a quality information and there are a lot of popular and folk not copyrighted informations available on researches. All the other options apply to the question because they are the synthesis of a good research, they must be "relevant" to the subject, "reliable" for both parts who does and reads it, and "easy to find" for people to keep on the track of the research by re-reading it, researching even more, and checking informations.
