Answer:
4 sides
Explanation:
A lot of math is about pattern matching. Here, you're asked if sides are the same length (one side matches another), if there are right angles (square corners), and if the number of angles or sides is 4.
You might make the observations ...
pink: 2 pairs of parallel sides that are the same length (4 sides). Adjacent sides are different length.
orange: all 4 sides are congruent and at right angles
blue: 2 pairs of parallel sides that are the same length (4 sides). Adjacent sides are different length.
green: 2 pairs of parallel sides that are the same length--4 sides and 4 right angles. Adjacent sides are different length.
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The only feature in common is "4 sides."