The correct answer is 'its way of challenging social norms'. Because in this play, a woman decides to leave her husband and children, which was, of course, unacceptable at the time.
A Doll's House discusses the traditional 19th century marriage. What Ibsen did in the play was considered controversial during those times. The play became significant for the depiction a woman's lack of opportunity in finding her place in a male-dominated society. Because of its criticism of social norm during that time it became so popular, but also controversial at the same time.
