Answer:
B. Everything purchased from Europe meant less money for the northern states.
Step-by-step explanation:
Let's break it down...
It can't be D, because while the north wasn't exactly besties with Europe, they were still a powerful group that America needed to stay in contact with.
(They were after all a new country)
It can't be C, since that wouldn't affect slavery unless they were directly purchasing people.
As for B, it is a probable answer. This is because if the northern states are manufacturing something, purchasing it from Europe would in fact be damaging for their economy.
A doesn't make a lot of sense. This is because while it COULD be applicable, it isn't very good reasoning.
This leaves us with B, the most likely answer based on the given information. Hope this helps!