To solve for \( m∠A \) when \( m∠C = 75° \), we use the properties of angles formed by two intersecting lines. The angles around the intersecting point sum up to \( 360° \), and for two adjacent angles, they are supplementary, meaning they add up to \( 180° \).
Since angles \( C \) and \( A \) are opposite angles, they are equal:
\[ m∠A = m∠C \]
Thus, if \( m∠C = 75° \), then:
\[ m∠A = 75° \]
Therefore, the correct response is:
75°