听力原文：Money from migrant workers now exceeds the combined total of all direct foreign investment and foreign aid to Latin America -- 62.3 billion dollars. 23 billion dollars of that was sent back to Mexico, mostly from workers living in the United States. It now ranks along with oil and tourism as Mexico's biggest foreign currency earner. The Inter-American Development Bank, which supports the region with aid and other help, says the remittances, as they're known, will increase by about fifteen percent a year during the next four years, topping one-hundred billion dollars by 2010. The bank describes the money as a very effective poverty reduction programme because it keeps between eight and ten million families above the poverty line. But it says it also means the economies of the region are not generating enough jobs to keep workers from leaving in the first place. Another problem is that as much of the money is sent back in small amounts, it's difficult to track. The average is between a hundred and a hundred-and-fifty dollars a month. That in turn makes it an unpredictable source of revenue for governments to tap into. The bank says it wants people to get away from what it calls cash to cash flows and into account to account transfers but the bank says the recent crackdown on illegal immigrants by the American authorities could hinder efforts to get migrants to use banks.
The passage is about ______.

A. migrant workers
B. poverty reduction
C. remittances
D. Latin America