Which of the following pairs of angles is supplementary?

• A. $60°$ and $120°$
• B. $30°$ and $60°$
• C. $90°$ and $90°$
• D. $45°$ and $45°$

Answer: (C)

Verified step by step guidance

1. Recall the definition of supplementary angles: two angles are supplementary if the sum of their measures is exactly \$180^\circ$.
2. Check the first pair: \$60^\circ\( and \)120^\circ\(. Calculate their sum: \)60^\circ + 120^\circ$.
3. Check the second pair: \$30^\circ\( and \)60^\circ\(. Calculate their sum: \)30^\circ + 60^\circ$.
4. Check the third pair: \$90^\circ\( and \)90^\circ\(. Calculate their sum: \)90^\circ + 90^\circ$.
5. Check the fourth pair: \$45^\circ\( and \)45^\circ\(. Calculate their sum: \)45^\circ + 45^\circ\(. Identify which pair sums to \)180^\circ$ to determine the supplementary angles.