We need to find the area for a square. To do this we will use the following expression:
![\text{Area = l}^2](https://img.qammunity.org/2023/formulas/mathematics/college/62ltrmnop7fdinpag1015c9osgjjc0c7fa.png)
Where "l" is the length of the side of the square. Since this square has 12 feet in length, then it's area is:
![\text{Area = 12}^2=144\text{ square ft}](https://img.qammunity.org/2023/formulas/mathematics/college/l51zzelangctclm7qo86iyvr9q2ap5syad.png)
The area of the square is 144 square ft. The correct option is b