题目

Some people believe that a Robin Hood is at work, others that a wealthy person simply wants to distribute his or her fortune before dying. But the donator who started sending envelopes with cash to deserving causes，accompanied by an article from the local paper, has made a northern German city believe in fairytales (童话） The first envelope was sent to a victim support group. It contained 0,000 with a cutting from the Braunschtveiger Zeitung about how the group supported a woman who was robbed of her handbag； similar plain white anonymous (匿名）envelopes, each containing 0,已知a=1.70.9，b=0.91.7，c=1，则有（ ）A．a＜b＜cB．a＜c＜bC．b＜a＜cD．b＜c＜a