The answer is the complexity of outcomes from action versus inaction. Hamlet is tortured by his own contradictory thoughts an beliefs, he analyses every little thing that happens around him.
Incorrect option the mystery of love and commitment between couples. Even when love is very present for his relationship in the story it is not the main topic of it
Incorrect option marriage as the ultimate goal of life. the topic is mention in a minimal part of the story and as a very superficial one.
Incorrect option the difficulties and tragedy of war. Many of Shakespeare plays are based in war times and in this case even when it frames the general atmosphere it doesn't represent the main theme of the story.
Answer:
I think the answer is B), Because the only reason the author would add that evidence is because it's showing that today, birds could spread another disease just like the Spanish flu. Hope this helped :)
Hope it helps!
<em> ItsNobody</em>