Which of the events in the “causes” column do you think had the strongest impact on enslaved african americans? explain why ?

I would honestly say that the "effects" are a bit hard to understand, however, the best choice I could give you is the very first one. Fugitive slave act. I say this because this is one of the only ones that affected a larger spectrum of African Americans, and not limited down to one state or Person.

monasticism. people often do monasticism in monasteries

the answer to your question is a. the salt plains

in 1811, he led an expedition, known as the george c. sibley expedition, to improve relations with the pawnee and kansa tribes, and also to locate the rumored jefferson's salt mountain