China’s central bank cut lending rates for the fourth time since November and trimmed the amount of cash that some banks must hold as reserves, stepping up efforts to support an economy that is headed for its poorest performance in a quarter century. The last time the central bank simultaneously cut interest rates and reserve requirements was at the height of the global financial crisis in late 2008. The latest move could also be aimed at comforting investors following a 20 percent plunge in the country’s stock markets over the last two weeks, some analysts said.