The correct answer is D.
Siobhan has already tried a variety of search strategies and has not been able to find the information she needs. At this point, it is a good idea for her to ask an expert for help. A professor or research librarian will be able to point her in the right direction and help her find the information she needs.
Giving up is not a good option, as the information Siobhan needs is likely out there somewhere. Looking in an encyclopedia is also not a good option, as encyclopedias are typically not up-to-date and may not have the information Siobhan needs. Trying to search on the dark web is a dangerous option and is not recommended.
The best option for Siobhan is to ask an expert for help. A professor or research librarian will be able to point her in the right direction and help her find the information she needs.