describe the set of points z in the complex plane that satisfy the given equation. |z−i|=2|z−1|

a) A circle with center at ( 3/5+i4/5 ) and radius 2
b) A circle with center at ( 1+i ) and radius 2
c) A circle with center at ( -i ) and radius 2
d) A circle with center at ( 1+i ) and radius 1