China’s ruling Communist Party began a key four-day meeting Monday to discuss how to further deepen reforms, state-run media said, with the world’s second-largest economy facing such challenges as a prolonged property sector crisis and population decline. The third plenary session of the 20th Central Committee, which brings together top party officials, is also expected to set China’s mid- to long-term economic policy. The country’s leader Xi Jinping delivered a work report and explained a draft decision of the committee on “further comprehensively deepening” reforms and advancing “Chinese mod…