A、They are especially intelligent. B、They are children’s favorite. C、They are quite easy to tame. D、They are clean and pretty. A

Six birds have just been trained to pick up rubbish at a French historical theme park. According to the park’s manager, Mr. Villiers, the goal is not just to clear up the park. He says visitors are already good at keeping things clean. Instead, he wants to show that nature itself can teach us to take care of the environment. He says that rooks, the chosen birds, are considered to be particularly intelligent. In the right circumstances, they even like to communicate with humans and establish a relationship through play. The birds will be encouraged to clean the park through the use of a small box that delivers a small amount of bird food each time the rook deposits a cigarette end or a small piece of rubbish. So far, visitors to the theme park have been excited to see the birds in action. However, some parents are concerned that it encourages their children to drop litter so they can watch the birds pick it up. Villiers is not concerned about this criticism. He maintains most of the feedback he has received has been overwhelmingly positive. He hopes now to train more birds.
5. What have six birds been trained to do at a French historical theme park?
6. Why were rooks chosen by the park manager?
7. What is the concern of some parents?