如图，数轴上所表示的不等式组的解集是(　　)

如图是市售某品牌牙膏包装盒上的部分说明，其主要活性成分单氟磷酸钠（Na₂PO₃F）是牙膏的常用添加剂一。实验表明牙膏中单氟磷酸钠的质量分数达到0.75%～0.80%时，防龋齿的效果较好。（计算结果保留小数点后二位）

C

    My grandfather Jack is 96 years old，and he has had an interesting life. He has travelled a lot in his life in the Far East. He visited the Taj Mahal in India and the Pyramids in Egypt. He hunted（狩猎） lions in Africa, and rode a camel in the Sahara Desert. He says the most beautiful place he has travelled to is Kathmandu in Nepal.

    Jack has married twice. His first wife died when she was 32. He met his second wife Maria while he was cycling round France. They have been married for 50 years, and they have lived happily in a small village since they got married.

    Jack says that he has never been ill in his life. The secret of good health, according to my grandfather, is exercise. He goes swimming every morning. He has done this since he was a boy. He also has a glass of wine every night！Perhaps that is his secret！