Why did kansas become the battleground over slavery?

it bordered native american territory.
it was the first time slavery tried to move into free territories.
it bordered the slave states of missouri and oklahoma.
there were no slaves living in the territory at the time.

Which suggests the most critical aspect of the peak oil theory? 1) controversy rages over rumors that the fracking lobby in washington has influenced the statistics. 2) supporters and critics argue endlessly over the rate of extraction and shape of the bell curve. 3) saudi arabia will soon have to begin fracking, leading to protests and further destabilization. 4) a new oil discovery means a fresh peak cycle, making that region the target of aggressors.