The World Bank on Wednesday cut its global growth outlook for this year and urged countries to “fasten their seat belts” as they adjust to lower commodity prices and a looming rise in U.S. interest rates. Kaushik Basu, the World Bank’s chief economist, said the Federal Reserve should hold off on a rate hike until next year to avoid worsening exchange rate volatility and crimping global growth. It said low commodity prices, especially the roughly 40 percent drop in oil prices since last year, had hurt commodity exporters more than anticipated.