US President-elect Donald Trump’s challenges to China on trade and Taiwan are rattling American companies who have long benefited from stable US-China relations. Trump jarred Chinese officials on Sunday by saying the United States did not necessarily have to stick to its long-standing position that Taiwan is part of “one China.” Beijing expressed “serious concern” about Trump’s remarks. Four US industry sources who follow China policy closely said they were unsettled by any suggestion of abandoning the “one China” policy, which they said had served the business community well for several decades, according to Reuters. The sources, who spoke anonymously, stressed the importance of stability for businesses. They said Beijing could retaliate against US companies that do business in China if Trump takes his tougher line too far.