1·It has now reached a point where a growing number of people believe that it is far too high, and that bringing it down will be one of the great challenges of the twenty first century.
现在，到了越来越多人认为它太高了的程度，而且使它降低将是21世纪最大的挑战之一。
2·It is the twenty-first Football World Cup.
这是第二十一届足球世界杯。
3·Seventeen civilians were hurt. Most are students who had been attending a twenty-first birthday party.
17名平民受了伤，其中大多数是参加一个21岁生日聚会的学生。
—— 《柯林斯英汉双解大词典》
4·The task facing medicine in the twenty-first century will be to redefine its limits even as it extends its capacities.
21世纪医学面临的任务将是重新定义其限制，即使它扩大了其能力。
5·Geothermal energy probably will not make large-scale contributions to the world energy budget until well into the twenty-first century, if ever.
如果可能的话，进入了21世纪之后，地热能才会对世界的能量预算做出大规模的贡献。
6·Russia is holding the twenty-first FIFA WORLD CUP now.
俄罗斯正在举办第21届世界杯。
7·They are celebrating their daughter's twenty-first birthday in the Garden Hotel.
他们正在花园酒店为女儿庆祝21岁生日。
8·Many doctors feel that this is a problem in the twenty-first century.
许多医生认为这是21世纪的一个问题。
9·Which country do you think will win the first prize of the twenty-first FIFA World Cup?
你认为哪个国家会赢得第21届国际足联世界杯的冠军？
10·At the beginning of the twenty-first century, he could note that UNESCO had joined him in this conviction.
在二十一世纪之初，他注意到联合国教科文组织已经同他一道对此深信不疑。