[theontheone]

I consider myself pretty strong at math (in university right now) and I was stumped by the vector space question. I never considered, actually, what domain scalars should be drawn from.

Wikipedia says "the scalars can be taken from any field, including the rational, algebraic, real, and complex numbers, as well as finite fields."

[throwawaymath]

Does Wikipedia actually say that? That's pretty misleading. For any vector space V defined over a field F, V is only closed under scalar multiplication using the scalars of F. You can't choose scalars from arbitrary fields for any given vector space. The scalars have to be chosen from the underlying field of the particular vector space.

[blattimwind]

Without context it isn't a well-posed question; the important context of that question is the teaching material itself, which would have introduced scalars as reals in this case (I assume), thus establishing what is meant by "obvious" or "usual" [object].