I have the following exercise: I have a list of subsets of $\mathbb{Z}[X]$ and have to say which of these are subrings and which are ideals; and if it is an ideal I have to specify a generator for the set.
What is not clear to me is, how the "specify a generator for the set" is meant, since I could very well take the subset itself and it will generate itself obviously (for example, two of those subsets are set set of all polynomials with even coefficients and the set of all polynomials and the set of all polynomials whose coefficients at the terms of degree $0$ and $1$ vanish).
Is there an implicit assumption one makes, when one says that a generator is to be specified ? For example, is this generator maybe supposed to be a minimal generator (w.r.t to inclusion) ?