Translation:The objects that you threw, you will pick them up.
Unfortunately Sitesurf can't modify anything because Duolingo decided to hire contractors to write this course based on the CEFR structure. Since then (February 2019), the ex-contributors have been banned from the working platform and can no longer write sentences, correct mistakes, correct hints, add missing translations...
The new tree has a ton of these sentences where they're now forcing users to type this French grammatical construct literally in English in an almost word for word translation. I would say your answer is correct, more correct than the suggested answer, because people don't speak like this in English.