[单项选择]
Life Expectancy in the Last Hundred Years
A hundred years ago, life expectancy in developed countries was about 47; in the early 21st century, men in the United States and the United Kingdom can expect to live to about 74, women to about 80, and these
(51) are rising all the time. What has brought
(52) these changes When we look at the life
(53) of peoplel00 years ago, we need to look at the greatest
(54) of the time. In the early 20th century, there were the acute and often
(55) infectious diseases such as smallpox. Many children died very young from these diseases and others, and the weak and elderly were always at risk.
In the
(56) world these diseases are far
(57) today, and in some cases have almost disappeared A number of
(58) have led to this: improvements in sanitation and hygiene, the discovery and use of antibiotics, which
(5
A. And
B. Therefore
C. In addition
D. Nevertheless