we know that
[area of a circle]=pi*r²
r=10 in
[area of a circle]=pi*10²-----> 100*pi in²
if 360° (full circle) has an area of------------------> 100*pi in²
45°-------------------------------> X
X=45*100*pi/360-----> x=12.5*pi in²
the answer is
the option B) 12.5*pi in²