Let's analyze each statement:
A. The sum of the measures of two supplementary angles is 180°.
- This statement is always true. By definition, supplementary angles are two angles whose measures add up to 180°.
B. The sum of complementary angles is 180°.
- This statement is never true. By definition, complementary angles are two angles whose measures add up to 90°.
C. Two adjacent angles are complementary.
- This statement is sometimes true. Two adjacent angles can be complementary (add up to 90°), but they can also be supplementary (add up to 180°) or neither. Therefore, it is not true in all cases.
In summary: A. Always true B. Never true C. Sometimes true