The National Archives contain information so ----
that researchers have been known never to publish
because they cannot bear to bring their studies to an
end.外教的解释:
Means that people who do their research at the national archives like the information so much that they never want to stop researching so they never publish their work。
When i read the sentence i choose b rather that a because of the last part of the sentence "cannot bear..." meaning they find the information so interesting they dont want to stop their research. If this part of the sentence was not there then i think the answer would be a
The National Archives contain information so ----
that researchers have been known never to publish
because they cannot bear to bring their studies to an
end.这是纯正美国人的回答