今天刚开始做OG 11的逻辑就遇到困难! 请大家帮忙解决以下！！1 "Life expectancy" is the average age at death of the entire live-born population. In the middle of the nineteenth century, life expectancy in North America was 40 years, wherreas now it is nearly 80 years. Thus, in those days, people must have been considered old at an age that we now consider the prime of life. Which of the following , if true, undermines the argument above? A. In the middle of nineteenth century, the population of North America was significantly smaller than it is today. B. Most of the gains in life expectancy in the last 150 years have come from reduction in the number of infants who die in their first year life. C. Many of the people who live to an advanced age today do so only because of medical technology that was unknown in the nineteenth century. D. The propotion of people who die in their seventies is significantly smaller today than is the proportiion of people who die in their eighties. E. More people in the middle of the nineteenth century engaged regularly in vigorous physical activity than do so today. 我应该从哪里入手解这个问题呢？ | 
