we know that
the equation of a circle is
(x-h)²+(y-k)²=r²
where
(h,k) is the center
and r is the radius
in this problem (h,k) is (0,0)
so the equation is
x²+y²=r²
step 1
find the radius
substitute the point a (0,8) in the equation
0²+8²=r²------> r=8
step 2
find the circumference
C=2*pi*r-----> C=2*pi*8----> C=16*pi units
if 2*pi radians (full circle) has a length of--------------> 16*pi
1 radians--------------------------> x
x=16*pi/(2*pi)-----> 8 units
the answer is the option
A) 8
