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(       )

读《中东图》，回答下列问题

A: Mum, I have finished my homework .____ .
B: Of course .Which is your favorite TV program ?
A: Sports .It is said there will be a wonderful football match on TV tonight .
B: ____ 
A: A Chinese team will play against a Japanese team .
B: ____ 
A: I'm not sure . Ball games are usually shown on Channel 8.
B: ____ 
A:Well , it must be on Channel 6 then . Try that .
B: Here it is .____  Let's watch it together .
A: That's all right.