A:go outside
B:use the lift
C:crawl out
____ (judge) from his ____ (excite) news, his friends have found the key to ____ (solve) the problem.
已知圆C和y轴相切,圆心在直线x﹣3y=0上,且被直线y=x截得的弦长为27,求圆C的方程.