Lucinda wants to build a square sandbox, but she has no way of measuring angles. Explain how she can make sure that the sandbox is square by only measuring length.
A. Arrange four equal-length sides so the diagonals bisect each other.
B. Arrange four equal-length sides so the diagonals are equal lengths also.
C. Make each diagonal the same length as four equal-length sides.
D. Not possible; Lucinda has to be able to measure a right angle.