Let θ be the angle. Then we must have that

Of all the options, the only one that satisfies the condition above is (3π)/7
Hence, θ = (3π)/7
Therefore the angle for point B is (3π)/7
In the case of point A we must have that

In this case, the only possible angle is π / 5
Therefore the angle for point A is π / 5
In the case of point C we must have that

In this case, the only possible angle is (4π) / 3
Therefore the angle for point C is (4π) / 3