Historical context is looking at the information and thinking about the area it was made. If I say that 1,000,000 soldiers died that month in ancient Rome, your probably going to be really surprised and wanting to hear how. If I say 1,000,000 Russian troops died that month during WW2 you might not be as interested. Therefore the answer should be D. The social and economic conditions that surround it.
I hope this helps! :)