O is the center of an equilateral triangle A B C, F₁ , F₂ and F₃ are three forces acting along the, sides A, B, B C and A C as shown in figure. what should be the magnitude of F₃ so that the total torque about O is zero

• A

  (F₁ +F₂)/2

• B

  (F₁ -F₂)

• C

  (F₁ + F₂)

• D

  2(F₁ + F₂)