G-BJOP
I Can only emphasise what Mr Bucket says... They are not there to catch you out. There is always more than one way to skin a cat - something you will come to realise throughout your career.
Keep it simple, keep it 100% safe, and keep it fairly expeditious, and you cannot go wrong.
If you have gone totally in the wrong direction, you will be given the opportunity to amend your answer.. beware of being to easily swayed though!! If you think you have a safe, sensible answer, and you can explain why you think so (given your limited knowledge), you will be okay.
REMEMBER - They are looking for people to train to become ATCOs - they are not looking for ready made ATCO's.
Best wishes!