For what goods did foreign merchants visit the markets of axum to trade?

salt, gold, and ivory
silk, wine, and ivory
gold, ivory, and silk
wool, sheep, and oil

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.