G.B.C. interviewers will sometimes ask abstract questions. The nature of these questions is often philosophical, and they are often difficult to answer in even your native language. Practicing these questions in class will give you an edge and make sure these types of questions do not come as a complete surprise.
Your teacher will work through a range of abstract questions. They are difficult even for native speakers, and there is often no "right" or "wrong" answer. Try to talk about the topic rather than answer the question directly. Remember that showing off your English skills is the key to every G.B.C. test. These lessons will help you prepare for that.