根据短文内容，判断下列句子正误。

     Dick wants to buy some new clothes, so he goes to a shop. First he asks for some trousers and puts them on, but then he takes them off and gives them back to the shopkeeper and says, “No, give me a coat instead of(代替) these.” The man gives him a coat and says, “This one costs the same as the trousers.” Dick takes the coat and walks out of the shop with it . The shopkeeper runs after him and says, “You don't pay for (付钱)that coat !” “But I give you the trousers for the coat,”says Dick . “They cost the same as the coat, right?”

    “Yes,”says the shopkeeper, “But you don't pay for the trousers either(也).”

  “Of course I don't,” answers Dick, “I don't take them. I'm not a fool(傻瓜). Nobody gives things back and then pays for them.”

某农场开挖一条长480米的渠道，开工后，每天比原计划多挖20米，结果提前4天完成任务，若设原计划每天挖x米，那么求x时所列方程正确的是（ ）

人体形成尿液的器官是（　　）