In the oral exam you will be asked general questions about Evidence-Based Medicine:

For example: What is EBM?  Can you give a definition? What are its strengthen and weaknesses?

What types of study designs do you know? How are they different? What different clinical questions do they answer? The link to the paper Pros and Cons gives a detailed overview of the strengths and weakness to help you answer these questions. The resources links are also very recommended.