How to model a multiple relation situation?
I think this is the best way to model the data, and it lends itself very well to how Craft work. 

I guess the only reason to go with the Matrix approach instead, would be to ease how the information is published in the control panel. In some cases it might be easier to just publish one question with all the answers, instead of one question and all the answers seperately. But it's hard to say, not knowing the actual content and amount of data. 

It would definitely be possible to go for the Matrix solution too, but it might be a bit more complex to use in your templates, and maybe less efficient. But again, depends on your actual case.