I personally would pick A, and here's why;
B) Romeo And Juliet wasn't mentioned. The black flag part indicates tragedy, but never is Romeo and Juliet mentioned.
C) I can imagine that if they raised color coded flags, as opposed to big signs with letters on them, it was because they welcomed more than just literate nobles.
D) Never mentioned a t a l l . Unless there's a missing paragraph, electricity is quite irrelevant in this passage.
I hope that all helps :)