President Johnson decided not to run for re-election. The country was divided over the issue of the Vietnam war.
I believe it was the Arab Oil Embargo, because during this time we weren’t receiving as much oil so the speed limit had to go down to 55mph to preserve what we did have.
From what I can recall, the Adams-Onis Treaty more or less gave Florida to the U.S. but it did not exactly end the Second Seminole War, which can be made obvious with the fact that there are Seminoles still living in Florida. I don't remember the Treaty having anything to do with the British since this treaty was between Spain and the U.S.
Basically, I believe the answer is B.
It made settlement and transportation faster.
