The correct option is C a line whose equation is x+2y=0
equation of of the circles passing through the intersection of the circles x2+y2=1 and x2+y2−2x+y=0 is x2+y2−1+k(x2+y2−2x+y)=0
⇒x2+y2−(2kk+1)x+(kk+1)y−1=0
center of circle is (x,y)=(kk+1,−k2(k+1))
Therefore, locus is x+2y=0
Ans: A