Answer :- Option B is the right answer "Segment QR is the base, and segment TU is the altitude".
Explanation:-
The altitude or height of a parallelogram is the perpendicular line segment from the base to the opposite side (which may have to be extended) of the parallelogram. In the given figure, we can see that the altitude is TU=18 inches which is perpendicular to the base QR=20 inches.
Thus , option B is the correct answer. Segment QR is the base, and segment TU is the altitude.