For the best answer i would go with D
Hope this helps ;)
The correct answer is B: The murder of Polonius by Hamlet
This plot event accounts for the change in Laertes's character. At the beginning of the play, Laertes is a calm, gentle and docile person. However, after his father, Polonius, is murdered by Hamlet he returns to Denmark in order to avenge his father's murder. So, we can see that from Act I to Act IV Laertes's character changes dramatically as he becomes vengeful and he isn't a law-abiding citizen any more.
The second alternative is correct (B).
"Gold in California ignited interest in a railroad to reach the West. However, Americans disagreed on where to build the railroad."
The use of the conjunction "however" in this context connects the two sentences with a contraposition, giving the exact meaning for the continuity of the text. In this way, it became clear that there was a need to build a railroad, but there was no unity among Americans about where to build the railroad.