# Flip flop

How many of the following 8 shapes must have (at least) one axis of symmetry?

$\begin{array}{c}&&\text{equilateral triangle}, &\text{right triangle}, &\text{square}, &\text{cyclic quadrilateral}, \\ &\mbox{parallelogram}, &\text{rhombus}, &\text{rectangle}, &\text{regular pentagon} \end{array}$

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