In twenty-first Century, the human has entered information age.

　　21世紀(jì)，人類已經(jīng)完全進(jìn)入了信息化時(shí)代。

　　Knowledge economy will play a leading role in the twenty-first century.

　　21世紀(jì)是知識(shí)經(jīng)濟(jì)占主導(dǎo)地位的世紀(jì)。

　　The twenty-first century is a time of development, challenges and competition.

　　二十一世紀(jì)是一個(gè)發(fā)展的時(shí)代、挑戰(zhàn)的時(shí)代、競(jìng)爭(zhēng)的時(shí)代！

　　Some people have a big party for their twenty-first birthday.

　　一些人會(huì)在他們21歲生日舉行盛大的聚會(huì)。

　　In twenty-first Century, population aging is a global phenomenon.

　　21世紀(jì)的今天，人口老齡化已經(jīng)是全球化的現(xiàn)象了。