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: Surgery
Most useful investigation in sliding hernia in female - 
Select and explain. 
A. Fluoroscopy, B. Barium-meal, C. Palpation method, D. Ultrasound
B: Barium-meal
Answer: B: Barium-meal 
Explanation: • The hernia may be visible on a plain radiograph of the chest as a gas bubble, often with a fluid level behind the heart.
• A barium meal is the best method of diagnosis.
• The endoscopic appearances may be confusing, especially in large hernias when it is easy to become disorientated.