A body executes simple harmonic motion. At a displacement x, its potential energy is U₁. At a displacement y, its potential energy is U₂. What is the potential energy of the body at a displacement (x + y )?

A. U₁ + U₂
B.( √U₁ + √U₂)²
C. √U₁ + U₂ ²
D. √U₁² + U₂²