Tesla's electric-vehicle registrations in California dropped 15.1 per cent during the first quarter, according to industry data, signaling an accelerated decline and growing challenges for the Elon Musk-led automaker in the crucial U.S. market. The company's quarterly sales globally fell 13 per cent to the lowest in nearly three years, hurt by a backlash against CEO Musk, rising competition and as customers wait for a refresh of its highest-selling electric vehicle Model Y. "An aging product