Choose the polygon that is a regular quadrilateral

"Regular quadrilateral" means it has four sides, and the
sides AND the inside angles are all equal.

-- The one at the upper left is a rhombus.  All 4 of its sides
are the same length, and the first time I saw it, I picked it.
But then I remembered that in order to be 'regular', the
inside angles also have to be equal, and in a rhombus,
they're not.

-- The one in the lower right is a square.  It has four sides,
they're all equal, and the inside angles are all the same too.
So the square is the only one that does the job for you.

I’m not sure what it is i sorry : ((