The Speaking Test Scenario:
Having finished the individual presentation in Task A you then go to Task B. After the two minutes preparation you should carry out the group discussion with the other candidates in the Speaking Test. In the group discussion you have to choose which of the four choices, as that of Candidates' A to D as the best for you to argue and and make your stand.
When you are doing the group discussion you might be in a difficult situation where you have to choose what topic is the best to support. It is not your obligation to choose which is the best topic for you to talk about. The examiners do not have a set of topics up their sleeves which you should correctly choose as "the best" topic. There is no such thing as the best topic which you must get it right, and if you do not get it right then you are penalised. No such thing!
The next best thing to do is how well prepared are you? In which choice of candidates' task are you very well prepared? If you are well prepared for your own task, then go ahead with it, full throttle in the discussion. If you like a task's subtopic but you are not well prepared for it then do not choose it to make your arguments as that will be sort of suicidal to do it. Just like venturing into the wilderness.
The best topic for you to choose is determined by you, the MUET Speaking Test 800/2 candidate. It is up to you entirely and the examiners are there to listen to how well your delivery is done. They want to listen to how you express yourself, your points, how you argue your points and whether you contribute to the discussion. They also want to observe your language proficiency, in terms of grammar, your diction and whether you use linkers/discourse markers and other speaking skills that you must have learned over the years you were in school. It is imperative that you show competence in your arguments and whether you are treating the discussion with a certain degree of acceptable standard of maturity.
One of the requirements in the syllabus is that you "show mature treatment of the topic". It does not matter which topic that you choose in your discussion as long as you give a sound argument with the appropriate choice of words and grammar proficiency. To put it in a nutshell it is you who determines the best choice of topic, not the examiners. The examiners are there to listen to you and give marks for your performance for your choice of topic under discussion.