The 23-year-old university student in Hangzhou, a city on China’s eastern seaboard, has a stock-market problem. Lu’s unwavering faith in Chinese policy makers illustrates the growing risk of moral hazard in the world’s second-largest stock market, an unintended side effect of government efforts to halt a $3.9 trillion selloff. The moral hazard problem is particularly acute in China because authorities stepped in at a time when stock valuations were still expensive, said Francis Cheung, a strategist at CLSA Ltd. in Hong Kong.