Let's analyze each of the options and discard the ones that doesn't apply to XW.
A perpendicular bisector in a triangle is a segment that is perpendicular to one of the sides and intercepts it right at its midpoint dividing it into two equal segments. As you can see XW divides YZ in two segments YW and WZ. However these two don't have the same length which means that XW is not a perpendicular bisector.
An angle bisector is a segment that divides an angle into two angles of equal measure. XW divides the angle YXZ into two angles: YXW and WXZ. As you can see the later clearly has a smaller measure than the former so XW is not an angle bisector.
The median of a side of a triangle is a segment that connects its midpoint with its opposite angle. XW connects side YZ with its opposite angle but not through its midpoint as we saw before. Then XW is not a median.
The altitude of a triangle deppends on the side we use as reference and is given by a segment perpendicular to this side that connects it with its opposite angle. Angle YXZ is the opposite angle of side YZ and XW is perpendicular to YZ so it is an altitude.
AnswerThen the answer is option D, altitude.
