20th century is a century of flying be expanding by leaps and bounds development of the productivity, and is a century of ecology environment deteriorated.
20th century is a century of flying be expanding by leaps and bounds development of the productivity, and is a century of ecology environment deteriorated.
摘要20世纪是社会生产力飞速发展的世纪，也是生态环境空前恶化的世纪。