"남자는 모자를 주웠어요."
Translation:The man picked up a hat.
모자 can mean hat or cap, but the computer will not accept cap. Also, nothing in this sentence says he picked up HIS hat. If he is in a store to buy a hat, the sentence could mean the man picked up a hat. "A man picked up a hat" or "A man picked up his hat" should also be accepted since Korean does not specify the definite article.