Which of the following pairs of angles are supplementary angles?

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

Answer: (C)

Verified step by step guidance

1. Recall that supplementary angles are two angles whose measures add up to \$180^\circ$.
2. Check the sum of the first pair: \$30^\circ + 60^\circ = 90^\circ\(. Since \)90^\circ \neq 180^\circ$, these are not supplementary.
3. Check the sum of the second pair: \$60^\circ + 120^\circ = 180^\circ\(. Since the sum is exactly \)180^\circ$, these angles are supplementary.
4. Check the sum of the third pair: \$90^\circ + 90^\circ = 180^\circ$. These angles are also supplementary.
5. Check the sum of the fourth pair: \$45^\circ + 45^\circ = 90^\circ\(. Since \)90^\circ \neq 180^\circ$, these are not supplementary.