The expert predicted that America's gross domestic product will return to more than 3 percent yearly expansion. For example, Dow Chemical is investing $4 billion in Texas plastics production that will be operational by 2017. Such growth requires cheap oil and natural gas -and by 2020 or so, the United States will surpass Saudi Arabia in oil output, and Russia in gas. He continued: 'The big attraction is the low price of natural gas, the lowest-carbon fossil fuel, which can be produced profitably at about a third the price per unit of energy as other hydrocarbons. That is particularly attractive to chemical companies. It is the raw material for plastics, Styrofoam, tires, sealants, adhesives, films, liquid crystal screens, nylons, polyesters -nearly everything around us. ' In this passage, what's going to cause America's future growth?