in the given triangle,
AB = BC = 6
As, the two sides are equal so, the given triangle is isosceles.
also, the angle < ABC = 120 degrees,
the area of the isosceles triangle is,

here a = length of two congruent sides,
theta = the angle between congruent sides.
put the values,
A = 1/2 x 6^2 x sin 120

![\begin{gathered} A=(36)/(2)*\frac{\sqrt[]{3}}{2} \\ A=9\sqrt[]{3} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/wt8qingec9jr0fdm3pa7yjkqo92axb9mu4.png)
thus, the correct answer is option D