E
I
Letters that have parallel line segments are H, E, F, M, and N
C. I. H. F.
The letter - H
A regular hexagon has three sets (pairs) of parallel line segments that form it.
They can not be line segments on the same line, but they can both be line segments.
The answer depends on the font being used. In a serif font a lot more characters will have intersecting lines. So the answer is likely to be a subset of the upper case sans serif letters C, I , J, O, S. But even here, the letter O does have parallel segments, and possibly C as well.
In the upper case Roman alphabet they are: C, I, J, O and S. However, in the case of C, O and S, there are parts of the curved segments which are parallel.
how many pairs of parallel line segments does a stop sigh have
There is no specific name - other than what you used: "a pair of parallel line segments".
E , f , h , i, Z, U, , N
Which pair. Of line is parallel fghj