Answer: A. 42 feet
Explanation:
If a square has a perimeter of 28 feet, then each side would be 7 feet long because a square has 4 equal sides.
So if they are joined together to make a rectangle, the short side would be 7 feet long and the longer side would be 14 feet long.
You then add all the sides together so:
7 + 7 + 14 + 14 = 42 feet