I was also very confident based on the category - and I mean, there were only 6 shuttles, so I thought odds were good I could figure it out.
I didn't know that fact about Endeavour and Discovery - but somehow knew those were the two shuttles in question. I hadn't the foggiest idea, however, who the explorer might be, and so went with my default "No-idea-which-explorer" answer, which happens to be Cook (I did a project on him in grade 3, and don't remember much about him at all).