Question

X centered at the origin with radius of 10

Answer 1

the complete question in the attached figure

we know that

the equation of a circle is
(x-h)²+(y-k)²=r²
where
the center is the point (h,k)

if the center is the origin with radius of 10
then
(h,k) is (0,0)
r=10 units
so

(x-0)²+(y-0)²=10²----------> (x)²+(y)²=100

the answer is the option 
A. x2 + y2 = 100