已知圆C的圆心是直线 x-y+1=0与x轴的交点，且圆C与直线3x+4y+13=0 相切，求圆C的方程．

— What do you think of the furniture on exhibition?  

— Well, great! But I don't think much of ______ you bought.   [      ]

A. the one      

B. it       

C. which        

D. that