Translation:Try on the hanbok.
입다 here is “irregularly regular” since it is one of the few -ㅂ verbs/adjectives that do not undergo a root change. The other ones that do:
• 춥다→추우세요 (cold)
• 돕다→도우세요 (help)
Why isn't "Try on a hanbok" accepted as correct? Couldn't it be either "the" or "a" in this case?