Which of the following best describes supplementary angles?

• A. Two angles whose measures add up to $180°$
• B. Two angles whose difference is $90°$
• C. Two angles that are equal in measure
• D. Two angles whose measures add up to $90°$

Answer: (A)

Verified step by step guidance

1. Understand the definition of supplementary angles: Supplementary angles are two angles whose measures add up to 180 degrees.
2. Recall that the sum of the measures of supplementary angles can be expressed as an equation: \(\text{Angle}_1 + \text{Angle}_2 = 180^\circ\).
3. Compare this definition with the given options to identify which one matches the condition of adding up to 180 degrees.
4. Note that options mentioning sums or differences of 90 degrees or equality of angles do not satisfy the definition of supplementary angles.
5. Conclude that the correct description of supplementary angles is: Two angles whose measures add up to \$180^\circ$.