There is a horizontal film of soap solution. On it a thread is placed in the form of a loop. The film is pierced inside the loop and the thread becomes a circular loop of radius $R$. If the surface tension of the loop be $T$, then what will be the tension in the thread

After piercing the film inside the loop, soap film remains only outside the thread. A soap film has two surfaces, so the pull due to surface tension on the thread per unit length is $2T$ directed normally outward. For a small element of the circular thread subtending angle $d\theta$, if the tension in the thread is $F$, the inward resultant due to thread tension is $F\,d\theta$. The outward force due to surface tension on that element is $2T\,(R\,d\theta)$. In equilibrium, $$F\,d\theta = 2T R\,d\theta$$ So, $$F = 2RT$$ Now compare with the options: this matches option $D$.