老龄化为什么会成为问题根据研究，世界上的人口老龄化是历史上未曾出现的社会现象。从根本上讲，这种人口转变是医疗进步、教育水平明显提高和经济发展的直接成就。近年来，健康老龄化的观念日益受到国际社会的关注。

A. UN gives priority to peaceful settlement of the conflicts among countries
B. the peacekeeping troops are most powerful in the conflicts between countries
C. economic sanction will be imposed on the countries involved in war
D. joint military action is the last resort of the Security Council in dealing with conflicts between among countries

A. mission
B. membership
C. rights
D. history

A. reuse
B. reread
C. rewrite
D. recite