Answer: B. 78
Explanation:
Given:
BC=CD
all the other sides of each triangle are radii, so they are all equal the 2 triangles are congruent.
>Both angles A =78
An angle from the radius is the same as the arc angle it creates.
The arc angle is double only if the angle touches the end of the circle not the radius. that's why it's not 156
So, <BAC =78 so arc angle BC=78