Answer:
B On the 25th March, 18-, a very strange occurrence took place in
St Petersburg.
Explanation:
If the question is about 'establishing a straightforward and matter-of-fact tone of the text' then you need to look for an answer that is...straightforward and matter-of-fact lol! I had to read this for school too, not long ago. If you read these options, the only one I'd consider matter-of-fact is B. It describes what was happening, where, and when. The others are all quotes from characters that in my opinion don't really fit to establish a straightforward tone of the text.