Any answer choices? It's hard to help without them.
It was principally the fact that the British Navy was carrying off American sailors and making them work for on the ship of British vessels during the Napoleonic Wars that caused the United States to carry out economic sanctions (commercial and financial penalties applied by one or more countries contrary to a directed country, group, or individual) against them.
Black holes themselves can not be seen, nor do they leave trails (since emptiness does not have to be caused by a black hole), but there is evidence for black holes: scientists can see the effects of their gravity on nearby stars. The answer is B.
When the african americans moved to the north that was called immigration