问题补充：单选题 与直线x-y-4=0和圆x2+y2+2x-2y=0都相切的半径最小的圆的方程是?
A.(x+1)2+(y+1)2=2
B.(x+1)2+(y+1)2=4
C.(x-1)2+(y+1)2=2
D.(x-1)2+(y+1)=4
答案：C