Quadrilateral abcd is inscribed in the circle. which sentence is true?
a) a and b are supplementary
b) a and c are supplementary
c) m∠a = m∠b
d) m∠c = m∠d

The true statement on Quadrilateral ABCD is B) A and C are supplementary. The theory is that when a quadrilateral is inscribed in a circle, the value of opposite angles always adds up to 180 degrees. The summation of two angles resulting to 180 degrees is called supplementary angles.

Definitely