After the civil war, the cost of living decreased because
a. consumers wanted imported goods.
b. sanitation and medical care improved.
c. men took public transportation to work.
d. technology made manufacturing more efficient.

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.