The anwser c should be correct
Number 18 would be "D".
Number 19 would be "A".
Number 20 would be "C".
Number 21 would be "C".
Number 22 would be "D".
Number 23 might be "C" I'm not sure, lol.
I think the answer would be reassure white american settlers that the frontier was safe and peaceful.
Hope this helps