Why are more and more people diagnosed with cancers today? 
Why are more and more people diagnosed with cancers today?A、People nowadays have more bad habits.
B、People nowadays enjoy longer life expectancy.
C、People nowadays are exposed to more sources of stress.
D、People nowadays are more vulnerable psychologically.
【正确答案】：B
【题目解析】：目的原因题。A、C、D选项是第一段提到的常见的引发癌症的原因，所以都不是题干的答案；从第二段第二句话开始描述寿命越长引发的疾病，所以B选项是正确的。