BEIJING — China’s third-quarter GDP grew a disappointing 4.9% as industrial activity rose less than expected in September.The National Bureau of Statistics said Monday that gross domestic product grew 4.9% in the third quarter from a year ago. That missed expectations for a 5.2% expansion, according to analysts polled by Reuters.Industrial production rose by 3.1% in September, below the 4.5% expected by Reuters. “Since entering the third quarter, domestic and overseas risks and challenges have increased,” Fu Linghui, spokesperson for the National Bureau of Statistics, said at a press conference Monday in Mandarin, according to a CNBC translation.cnbc.com