Answer: AB || DC (1st choice)
Reason:
- Angles A and D add to A+D = 59+121 = 180
- Angles B and C add to B+C = 37+143 = 180
We have two pairs of consecutive interior angles that are supplementary. We then use the converse of the consecutive interior angles theorem to conclude side AB is parallel to DC. This means ABCD is a trapezoid.
Refer to the diagram below.