短文理解 听力原文： Credit card fraud is a big problem. Card fraud in the U.S. involving bank cards alone totaled $ 680 million last year, which represented an increase of more than 35% over a 10-year period. However, the tide is beginning to turn, and the growth percentage of fraud is diminishing technologies are becoming more widely used. In 1994, Visa card fraud in the U. S. was as new equal to the figure posted in 1992. At Master Card, bogus card transactions rose 14% from 1993 to 1994. Even so, the growth rate has slowed considerably from the beginning of the decade. That looks good news for bankers and for average card holders as well. 21. What is the passage mainly about? 22.How much did bank card fraud involve in U.S. last year? 23.What conclusion can we draw concerning card fraud? (21)