China’s exports unexpectedly fell 6.4 percent in April from a year earlier, while imports tumbled by a deeper-than-forecast 16.2 percent, fueling expectations that Beijing will quickly roll out more stimulus to avert a sharper economic slowdown. The dismal trade performance raises the risk that second-quarter economic growth may dip below 7 percent for the first time since the depths of the global financial crisis, adding to official fears of job losses and growing levels of bad debt.