下列四个图形中，既是轴对称图形，又是中心对称图形是（　　）

    In our city there is a big zoo. There are a lot of different animals in it. There are some scary（可怕的） tigers and lions. They like eating meat and they eat much meat every day.

    There are also two big elephants and a baby one. Children like to ride(骑) one of them. The elephants are very kind and friendly. They eat much grass and bananas.

    In the zoo, we can see different kinds of bears, black bears and white bears. They are heavy(沉重的) . They are all slow and clumsy . They stand on their back legs and lift their front legs to ask for food. They like cakes very much.

    Do you like pandas? There's only one in the zoo. Her name is Huahua . She is very cute. She likes eating bamboo a lot. She is kind of shy. She's very interesting and lovely.

 2015年6月10日，北京市向国际奥委会申请举办2022年冬奥会．冰上运动场馆的外墙将采用新型的塑料膜材料聚氟乙烯（C₂H₂F₂）_n，它美观耐用，使用寿命达15年以上．关于聚氟乙烯的说法错误的是（　　）​