【正确答案】 C

【答案解析】[听力原文]
   Falling oil prices, China's economic slowdown, and a pessimistic outlook for the overall global economy this year has sparked another sell off of stocks on global markets. U.S. indexes fell 3.4 percent or more in Wednesday's afternoon trading.
   The United Nations foresees a slight improvement in world economic growth over the next two years. Lisa Schlein reports.
   "The world economy grew by a mere 2.4 percent in 2015. U.N. economists say they expect a modest improvement over the coming two years, with global growth reaching 3.2 percent at the end of next year. The U.N.'s joint report predicts growth in developed economies will continue to gain momentum this year, surpassing 2 percent for the first time since 2010. It says developing and transition economies are expected to do even better with growth rates reaching 4.3 percent in 2016 and 4.8 percent in 2017."
   How much did U.S. indexes fall in Wednesday's afternoon trading?
数字听力题。由画线句子可知，美股指数在周三下午的交易中下跌3.4%或更多。故答案为C。