This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
The main action of muscle "obturator externus muscle" is? 
Select and explain. 
A. Medial rotation of thigh, B. Lateral rotation of thigh, C. Flexion of thigh, D. Extension of thigh
B: Lateral rotation of thigh
Answer: B: Lateral rotation of thigh 
Explanation: Obturator externus muscle attaches to the external surface of the obturator membrane, adjacent bone, and trochanteric fossa. The obturator externus muscle laterally rotates the femur at the hip joint. The obturator nerve (L3 and L4) innervates this muscle.