Problem Solving (PS) | The points R, T, and U lie on a circle that has radius 4. If

Length of arc RTU=4π/3
Angle subtended at the centre=\(\frac{4π}{3}\)/(2π*4)*360 =60 deg.
In triangle RCU, radius, RC=CU=4, hence each angle is 60 deg and triangle is equilateral triangle.
Hence RU=4
Answer D.

---