Note that in a standard equation of a circle :
[tex](x-h)^2+(y-k)^2=r^2[/tex]The center is at (h, k)
From the problem, the given equation is :
[tex](x-1)^2+(y-2)^2=4[/tex]The center is at (1, 2)
The only option that has a circle centered at (1, 2) is A
The answer is A.