To show that 4 points are the vertices of a square, which of the following must be shown?

A square has four equal sides and two equal-length diagonals. Showing only equal sides could also describe a rhombus, which need not be a square; showing both properties identifies the square. Therefore, the best answer is “All sides are of equal length and the diagonals are of equal length.”

AI-written and checked against the verified answer.