C) Maryland leaving the Union would mean that Washington D.C. would be surrounded by Confederate territory.
Explanation:
Option A is not correct as Kentucky and Missouri for example were much larger.
C is correct because if they have lost Maryland, Washington will be at reach of Confederate troops, and that would meant that president and government will have to leave it.
D is not correct as there is no reason to conclude that this would have happen.
the black plague seemed to go away during the winter time because all the rats and fleas would freeze to death and be dormant and not move till the spring and summer times