Battery-driven economy, is a much more expensive proposition. >> do oil companies worry about challenges to their supremacy coming from technology in some unexpected way? >> they do, exxonmobil studies the problem systematically. they're not afraid of most of the alternatives that are on the horizon, but they do worry, a little bit, about breakthroughs in battery technology. because great batteries could change the way we drive and make oil much less relevant as a transportation fuel. >> thank you, steven call. up next, is oil and its kissing cousin, natural gas, here to stay, climate change...