A is the right answer. The argument builds its case of connection between helping others and increasing life span. A says both properties are related to another host - woman.
This is a typical correlation and causation question.
When two things - A and B - happen together, it could be
1) A causes B
2) B causes A
3) c causes both A and B
-- by 会员 sdcar2010 (2011/3/10 12:08:32)