Answer:
QR, RS, QS
Explanation:
Based on answer choices, we suspect the missing vertex label is Q. Then the green triangle is ∆QRS. The line segments naming the sides of this triangle will have letters from this set of letters:
QR, RS, QS
_____
Comment on segment names
In a general polygon, the sides are named by adjacent letters in the polygon name. The first and last letters are "adjacent" for this purpose. For example, in polygon ABCDE, the sides are AB, BC, CD, DE, and AE. Of course, the letters naming any given side can be reversed. BA names the same side that AB does.