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
Which of the following is the best method to know the  depth of invasion in esophageal carcinoma 
Select and explain. 
A. Endoscopic ultrasound, B. CT, C. Contrast MRI, D. CECT
A: Endoscopic ultrasound
Answer: A: Endoscopic ultrasound 
Explanation: Ultrasound is used to know the t stage of cancer.