根据短文内容回答下列问题。

    One day, my wife and I went shopping. We took the car as we had a lot of things to buy, because my brother and his family were going to spend the weekend with us. We stopped the car in front of the shop. An hour later we came back to the car with a lot of things. Then the trouble(麻烦) started. We could not open the door.

    "Oh, dear," said my wife, "what are we going to do?"

    "Let's ask that policeman," I said.

    The policeman was very kind and glad to help us. Soon he got the door open. Just at that moment, an angry man came up and shouted. "What are you doing with my car?" We looked at the number of the car, and our faces turned very red.