As an engineer, we have loads of questions in our exams very similar, ie that sometimes you don't really know what they want from the question.
So my solution was to answer as best I could and enter on my rough work sheet everthing I knew about the systems in my own words (Sometimes diagrams) and submit it as a query.
A multiple choice template correction sheet doesn't do anyone justice so by having it written down as a query the examiner has to read what you've written and should give you credit for understanding the systems, theory etc.
Since Incorporating this method I've never failed an exam. I find it takes as long to write down all that as a query as it does to try and work out what they want from the question.