Answer:
Option D. 124°
Explanation:
step 1
Find the measure of angle AOC
The triangle AOC is an isosceles triangle, because OA=OC=radius
so

Remember that the sum of the interior angles in any triangle must be equal to 180 degrees

substitute the given values




step 2
Find the measure of arc AC
we know that
----> by central angle
we have

therefore

step 3
we know that
The inscribed angle is half that of the arc comprising
![m\angle ABC=(1)/(2)[arc\ AC]](https://img.qammunity.org/2021/formulas/mathematics/middle-school/ooqqomdkqmg0xjgj9ylp472viei05gf45r.png)
![m\angle ADC=(1)/(2)[arc\ AC]](https://img.qammunity.org/2021/formulas/mathematics/middle-school/9pwr65ig0evxd5z8tu9rexh06bkp8pupwz.png)
so

therefore
substitute the value of the arc AC