"The crying baby is cute."
Translation:우는 아기가 귀엽습니다.
A lot of work is left to do with regard to course consistency. If the desired ending is to be "어요" rather than "ㅂ니다" there needs to be some kind of a hint. Also, with regard to 이/가 or 은/는 there is inconsisency within the same set of questions. (this set as well as others) "The crying baby is cute." and "The sleeping baby is boring." should be expressed with the same particle for the purpose of his course, though in real life, there are situations where one would be more appropriate ovfer the other.
There is no desired ending. Both "-어요" and "-ㅂ니다" are good answers and accepted. The same applies to "이/가" and "은/는". I should say one of the purposes of these examples, or this course, is to expose learners to different words and different expressions; I don't see any point in using the same ending or particle over and over again just because the corresponding English expressions happened to have no difference in structure.
Korean words with the character ㄹ at the end of their stem are irregular. With many particles, when they are added, the ㄹ is dropped to make the word sound right when it is spoken.