Option A 84 m is the right answer.
Solution : The area of square is 144 m as given. Hence, the side of square is 12 m. The length of one smaller square in the shaded square is 6 m.
Hence the length of the rectangle is 6+6+6+6 =24
the breadth of rectangle is 6+6+6=18
The perimetre of rectangle is 2(l+b) = 2 (24+18) = 2*42 = 84 m