Question

Lucinda wants to build a square sandbox but has no way of measuring angles. Explain how she can make sure that the sandbox is square by measuring only length.
a.
Arrange four equal-length sides so the diagonals bisect each other.
b.
Arrange four equal-length sides so the diagonals are equal in length.
c.
Make each diagonal the same length as four equal-length sides.
d.
This is not possible; Lucinda has to be able to measure a right angle.