A triangle that is considered equilateral has

only two sides with the same measure

two sides that are perpendicular

all three sides congruent

two sides that are parallel

Triangle cannot have 2 sides because as it has 3 angles and 3 sides.

It cannot have 2 parallel sides because it would need more than 3 sides in order to close the shape of that

Sides aren't perpendicular because in equilateral triangle all angles are equal to 60 degrees and not 90 degrees.

Equilateral triangle has all 3 sides congruent which means that the answer is third option.