"그 여자는 누구입니까?"
Translation:Who is that woman?
Its the formal ending for questions :) 입니까 and 습니까 are for questions, which one you use depends on whether the previous word ends with a vowel or consonant!
You use -ㅂ니까 after a vowel, which is why it is 입니까 in this case. (이다 + -ㅂ니까)
There's just one exception. Whenㄹ is the last consonnant it counts as a vowel ending; so 살다:삽니다/삽니까?
It is 이다 (to be) followed by -ㅂ니까, the interrogative ending. Simply, it is what 입니다 is in a question.
I think "Who is that girl?" should be accepted too, because technically 여자 means girl too.