Saying a lot while saying nothing at all

I can't really think of anything

In speaking tests like the G.B.C., you may get questions that you have never thought of before. You should say something intelligent, but you need time to think of what to say.

Sitting in silence is a bad idea, and so is saying non-word sounds like um, or ah. So to buy time, try starting with an empty opinion. Native speakers do this quite often. 

Consider the answer below. It isn’t supposed to be entirely serious. It’s prevarication—not answering or avoiding the question (like a politician might), but still talking about the topic. Of course, the content is unacceptable in terms of the information as there is none. But the language itself is perfectly good, and using some of these phrases is a good idea if you need a little time to think of exactly what you want to say in reply to the question.

This answer can address nearly any question, including your thoughts on a topic in the news or your opinion on a business matter. 

Well, that’s an interesting question, and I must admit, I haven’t really thought about it before. But if I had to give you an answer, I suppose I would have to say that the truth, as always, lies somewhere in the middle.

What I mean to say is that there are both advantages and disadvantages involved. I know that there will be some people who claim that the pros outweigh the cons, but it is just as true that there is a substantial body of support for the opposite view.

That is to say, opinion is divided on the subject, and this would explain why the discussion is ongoing.

It’s a difficult question to get to grips with, partly because there are many aspects to consider before we can form an opinion.

If we examine one side of the argument, it’s easy to see why proponents support the claim. However, the opposite camp also have a legitimate case when we look at what they have to say.

So, it's an interesting, complex question and I would have to look into it further in order to give a strong opinion either way. 

That is a long answer and in terms of grammar, it's quite sophisticated. In terms of content though, the speaker says absolutely nothing. If you were in a business meeting, it would be considered a very weak answer. 

However, the goal of speaking tests is not informational. You don't have to give a well-thought-out opinion. You should, however, give some kind of an opinion! Don't give an answer exactly like the one above, but do try using some of the paragraphs to kill time while you think about what to say in response to a tough question. 

If you are preparing for the G.B.C., then try using this technique in your next lesson.

to buy time—to get more time than what has been given, typically when asked a tough question.
prevarication—to speak but avoid a question; mislead; lie.
the pros outweigh the cons—when comparing pros and cons, both are substantial, but the pros are bigger/ better/ more important.
a substantial body of support—plenty of evidence in support of something.
the opposite camp—people who have the opposite view. 
to kill time—to do something that keeps you busy while you are waiting for something else to happen.