I think something is broken. There was no sound on this question, so I couldn't hear anything to type and had to say "can't listen". When it showed the correct answer, it reads: "They will be back in 1 hour. Meaning: The child loves the birds."
Both are correct and accepted. If your sentence was rejected it was not because of that. We cannot help much if you only give us one word. Please use the REPORT options that the bottom of the exercise page then post a comment so we know to look for it.
That way we can let you know the reason sentence was rejected.