根据短文内容，选择正确答案。
   It’s Sunday morning．There are many people in the park，some boys  are playing basketball．There are some girls under a big tree．They’re singing and dancing．What are those women doing? They are drinking tea．Look at the woman in a blue coat．Who's she? She’s my mother．She is talking to Lin Feng．Lin Feng is her student．He is a good student．He studies hard．He’s good at all the subjects． And he's friendly to all his teachers and his friends．

宿建德江

【唐】孟浩然

移舟泊烟渚，日暮客愁新。

野旷天低树，江清月近人。

已知圆C：（x﹣3）²+（y﹣4）²=1和两点A（1﹣m，0），B（1+m，0），m＞0，若圆C上存在点P，使得∠APB=90°，则m的最大值为（　　）