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 180º.
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.

Step-by-step explanation:

1) If all angles of a quadrilateral are right angles, then the quadrilateral must be a square. This is not true because the quadrilateral can also be a rectangle.

2) Two shapes are similar if and only if their corresponding angles are equal. This is true.

3) All quadrilaterals have four sides, and the sum of all angles in a quadrilateral is 180º. This is false because the sum of the angles is 360°

4) if the diagonals of a quadrilateral are perpendicular bisectors, then the quadrilateral must be a rhombus. This is true.

5) There are three vertices in a triangle, or there are four sides in a pentagon. This is false because a Pentagon has 5 sides.

6) Any two triangles are either similar or congruent. This is not true. Congruent triangles are always similar

Therefore, the true statements are 2 and 4