If the chord joining the points $(1,2)$ and $(2,-1)$ on a circle subtends an angle of $\frac{\pi}{4}$ at any point on its circumference then the equation of such a circle is

• A

  $x^2+y^2+6 x-2 y+5=0$
• Correct answer
  B

  $x^2+y^2-6 x-2 y+5=0$
• C

  $x^2+y^2-6 x+2 y+5=0$
• D

  $x^2+y^2+6 x+2 y+5=0$

Hence, the correct answer is option: 'B'.