1. By the end of the next century, a single city may have more than 100 million inhabitants.
    到下个世纪末，一个城市的居民就可能超过一亿。

2. But the cause of malaria remained unknown to 17th-century medicine, and so there was investigation by experiment.
    但对于17世纪的医学来说，疟疾的起因仍属未知，所以便通过实验来进行调查。

3. We live in the twentieth century.
    我们生活在二十世纪。

4. Who could have imagined, in the mid 1970s, for example, that by the end of the 20th century, computers would be as common in people´s homes as TV sets?
    举个例子吧，在20世纪70年代中叶又有谁能想得到在20世纪末的时候，家庭用的计算机会像电视机一样普遍?

5. The twentieth century is the century of planetary overcrowding.
    20 世纪是地球上人口过度拥挤的不安定的世纪.

6. The twentieth century is the century of planetary overcrowding.
    20 世纪是地球上人口过度拥挤的不安定的世纪.

7. The temple which the archaeologists explored was used as a place of worship from the fifteenth century B. C. until Roman times.
    考古工作者考察的这座庙宇从公元前15世纪直到罗马时代一直是祭祀祈祷的场所。

8. The body of one statue was found among remains dating from the fifteenth century B. C.
    其中有一尊雕像，她的躯体是在公元前15世纪的历史文物中发现的，

9. The development of such a telescope will be one of the great astronomical projects of the twenty-first century.
    而开发这样一台望远镜将会是21世纪天文学的一个重要的研究课题。

10. The famous monastery of St. Bernard, which was founded in the eleventh century, lies about a mile away.
    11世纪建造的著名的圣伯纳德修道院位于离山口1英里远的地方。