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.
D most African American wished to save their families from slavery, it was suggested by the Confederates however to use a slave army, this was scrapped because they where afraid that the slaves would rebel since they had weapons.
B
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