Which of the following statements is true of "Earth’s Ozone Layer"?

JB: After 30 years of steady decline, Earth’s ozone layer is thinner but seems to be stable. A ban on ozone-depleting CFCs is largely responsible. Computer modeling gives reason to hope for an almost full recovery of Earth’s ozone layer within 60 years. But this sort of modeling is difficult -- and its predictions aren’t iron-clad.
DB: And some models show the ozone layer could face a new threat -- from global warming. Drew Shindell, an atmospheric scientist at NASA’s Goddard Institute for Space Studies in New York City, talked with us about his computer models of climate.

In January, demonstrators in Mexico converged on the capital to protest the spiraling cost of tortillas, a Mexican national staple made from corn. In response, the country’s president, Felipe Calderon, signed an agreement to stabilize tortilla prices. President Calderon says the 13-point agreement is aimed at protecting Mexican families and the economy from further price hikes on corn. Mexican tortilla prices have skyrocketed more than 700 percent since 1994. Experts say this is due in part to increased demand for corn to produce ethanol.