参考答案

正确答案：B
解析：[听力原文]
What made people healthier and let them live longer lives in the middle part of the 20th century?
信息明示题。文章第四段指出，The middle part of the 20th century brought new ways to help get over diseases．．．They made people healthier and let them live longer lives．由此可知，B正确。