It is dark because Barnardo has trouble seeing the other guard.
This scene takes place at midnight and it is so dark Barnardo cannot see the other guard. Barnardo shows up for his shift, but he can't clearly make out who Francisco is. Francisco has the same problem because instead of answering Barnardo he tells him to identify himself first. They get it figured out and Barnardo begins his shift.
I think it would be A, because she could've kept it to herself but she was honest with him and gave it to him. I know for a fact the answer is NOT C or D. But i'm 95% sure it's A
Medicare deduction (Not 100% sure though)