Which pair of angles can be considered supplementary?

Supplementary angles are defined as two angles whose measures add up to exactly 180 degrees. In this case, the correct pair consists of one angle measuring 100 degrees and another measuring 80 degrees. When you add these two angles together, you get 100 + 80 = 180 degrees, which meets the criterion for being supplementary.

To further understand why the other options do not qualify: the first pair, with angles of 30 degrees and 60 degrees, sums to 90 degrees; the second pair, with two angles of 90 degrees, totals 180 degrees, which is indeed supplementary, while the third pair, each measuring 45 degrees, adds to 90 degrees as well. These last three do not suffice to meet the definition of supplementary angles, making the combination of 100 degrees and 80 degrees the only correct answer.