Final answer:
The length of one side of Joseph's office is 12ft.
Step-by-step explanation:
To find the length of one side of Joseph's office, we need to find the square root of the area of the office. Since the area is given as 148ft², we take the square root of 148 to find the length of one side. The closest measurement to the square root of 148 is 12ft, so option C, 12ft, is the correct answer.