Thailand may be in a "middle income" trap. This means all but which of the following? Rising wages have undermined their comparative advantage in less-skilled labor-intensive exports. Once their economies reach a certain size, it becomes hard to find foreign buyers for their exports. O Capital-driven growth becomes unsustainable when countries relied on undervalued currencies. O An aging population leads to falling saving rates. O Investment in education is necessary to help the economy move up the value chain to produce more skilled-labor products