Which of the Following Statements BEST Describes the Function of the Piriformis

Which of the following statements BEST describes the function of the piriformis muscle?

A) Lateral hip rotator at all degrees of hip flexion/extension
B) Lateral hip rotator below 90° of hip flexion, medial rotator above 90° of hip flexion
C) Medial hip rotator at all degrees of hip flexion/extension
D) Medial hip rotator below 90° of hip flexion, lateral rotator above 90° of hip flexion