Technically, either one is fine as far as JavaBean conventions although "is" is preferable. I suppose that's good enough for the exam but don't take my
word for it. Others who are more savvy about the nuance in the context of the OCP exam will probably chime in. I still think that you need to consider grammar and semantics when you choose an answer, at least that's what I would do if I were taking the exam. It all depends on what name they give you in the exam, doesn't it?