A、1 ton. B、2.5 tons. C、8 tons. D、33 tons. A选项的内容表明，本题考查与重量相关的信息。短文中提到，2005年之前，在西非缴获的可卡因总量为1吨，故答案为A)。

A new report finds that West Africa has become a major hub of cocaine smuggling to Europe, a trend that threatens to undermine African countries as well as European law enforcement efforts.
    The report by the Vienna-based International Narcotics Control Board has found cocaine smugglers are choosing to ship drugs from South America to Europe, through West Africa and the Balkans.
    In the case of West Africa, Beate Hammond, an officer at the Board, says the findings are alarming. Hammond says that before 2005, the total amount of cocaine seised in West Africa was one ton. That has jumped to 33 tons the past three to four years.
    "Because the geographical location of West Africa makes it an ideal staging point for smuggling," Hammond said. "Then generally the structure, and law enforcement structures in particular, are very weak in African countries, and traffickers of course can take advantage of that."
    Hammond says Liberia, where 2.5 tons of cocaine were seised in January 2008, offers just one worrisome example.
    The study also says the price of cocaine has fallen drastically recently, possibly because shipping routes are cheaper and possibly because of the global economic downturn, although hard times may also lead to an increase in demand for the drug.
    Besides West Africa, Afghanistan remains a concern for drug enforcement agents.
    "Opium cultivation declined by more than 19 percent in 2008 and estimated production also declined," Beate Hammond said. "But this does not change the essential fact that Afghanistan remains by far the largest supplier of illicit opium poppy in the world and also the largest supplier of heroin."
Questions 22 to 25 are based on the passage you have just heard.
22. What does the new report find about West Africa, according to the passage?
23. What is the total amount of cocaine seised in West Africa before 2005?
24. What is a possible reason for the drastic falling of the price of cocaine, according to the passage?
25. Which country is the largest supplier of heroin?