原标题：美国敦促乌克兰下调征兵年龄下限，乌方：没必要
The 19th Group of Twenty (G20) Summit was held in Rio de Janeiro Brazil from Monday to Tuesday. In the face of geopolitical conflicts and economic uncertainties, the G20 Summit is expected to exert positive impacts and inject more stability into an unstable world, said Cui Shoujun, Professor and Director of the Institute of International Development Studies at the School of International Studies, Renmin University of China (RUC), in the W.E. Talk with China News Network.