5. Justin is helping his father build a rectangular sandbox for his little brother and sister. He has laid out the four sides of the sandbox, using two 8-foot boards and two 6-foot boards. Justin's father asks him how he knows he made the sandbox a rectangle. How could Justin reply? 8 feet A. "It has to be a rectangle. The opposite sides are the same length." B. "It has to be a rectangle. I measured the diagonals to be sure they were the same length." C. "It has to be a rectangle. I made sure that the two 8-foot boards are parallel and that the two 6-foot boards are parallel." D. "It has to be a rectangle because it is not a square." Valit of answers in the 6 fee​