Actually "그" would not generally be used in a natural Koran sentence to describe this situation. The woman who prepared the bed would have already been referenced in a prior sentence or would have been better described in this sentence. 미숙이 잠자리를 준비했다. "The" should not always be translated "그". The use of Pronouns is very different in the two languages,so Duolingo translations are often awkward. Also the English "articles" (a,an, the) often don't translate naturally into Korean.