I think the problem is that the 'lesquels' hints at an object rather than a person, and so the question is asking more like 'out of these objects, which ones are spanish?' than 'which of these people are spaniards?' I could be reading more into it than I should be though haha
I suspect you are spot on with your reasoning. I hasten to append that Spaniard can still be indirectly used to refer to an 'object' where a rank/position of employment takes the place of physical object. e.g.
- there are eight corporals in the courtyard, all of them armed
- that is sufficient, which ones are spaniards?
This is a limited example of course and only works because the object is simultaneously a person. Not a necessary piece of information to answer the question with, however people should always know when they have given a correct answer even if it has not been accepted, as was the case with bruces6.
There are a lot of true cognates throughout Duolingo, so the meaning is quite close to what it means in English. For example, café means coffee (or the place, which is actually borrowed from the French). However, there are some false cognates. For example, la piscine means pool - all the while, you can interpret that it means something other than "pool." Watch out for these, and pay attention.