Mr Smith 1from London. Now he is in China. He is 2 .He teaches 3 a middle school. He works very hard. His students like 4 very much. He can 5 a little Chinese . His students often teaches him Chinese 6 Sundays. Mr Smith likes playing football . He often plays football 7 his students.
   Mr Smith8  a son. His name is Jack. He is student. He studies in a middle school. He goes to school  9 bike everyday. He gets back home at four in the afternoon. He likes 10 TV in the evening.

若点B（a，0）在以点A（1，0）为圆心，以2为半径的圆内， 则a的取值范围为(       )