Answer:
The correct option is 4.
Explanation:
Given information: K is the center of the circle. AB is the diameter of the circle.
Angle subtended by a diameter is always a right angle. It the means the measure of that angel is 90 degree.

According to the angle sum property, the sum of interior angles of a triangle is 180 degree.
Using angle sum property in triangle ABC, we get



Therefore the measure of x is 15 degree. Option 4 is correct.