Which statement summarizes how the chart illustrates the author's position on ethanol?
a) the chart supports the author's claim that more corn used for ethanol means less corn for livestock.
b) the chart supports the author's claim that not only the price of corn, but the prices of wheat and soybeans have risen as well.
c) the chart supports the author's theory about why the price of corn has risen sharply in the last few years.
d) the chart shows that the history of agriculture has proven that corn prices will level out naturally.