People who give, live longer, studies have shown. Now, a new study by University of Michigan researchers shows that why people volunteer—not whether they volunteer—is what really counts.

Q: What does the new study mainly find?

How we volunteer makes sense to others.

How often we volunteer makes a difference.

Whether we volunteer decides our well-being.

Why we volunteer has an impact on our health.

细节理解题。根据第一段 “People who give, live longer, studies have shown. Now, a new study by University of Michigan researchers shows that why people volunteer—not whether they volunteer—is what really counts. (研究表明，乐于奉献的人更长寿。而密歇根大学的最新研究揭示：真正关键的因素不在于是否做志愿者，而在于为何做志愿者。)” 可知，新研究主要发现了我们做志愿者的原因会影响我们的健康。故选D。