Which statements are true?

if all angles of a quadrilateral are right angles, then the quadrilateral must be a square.

two shapes are similar if and only if their corresponding angles are equal.

all quadrilaterals have four sides, and the sum of all angles in a quadrilateral is 180°.

if the diagonals of a quadrilateral are perpendicular bisectors, then the quadrilateral must be a rhombus.

there are three vertices in a triangle, or there are four sides in a pentagon.

any two triangles are either similar or congruent.