从1870年到1940年，法兰西第三共和国一共更换了108届内阁，每届内阁平均存在时间约为8个月。造成内阁频繁变动的原因在于(    )

水螅和海葵是同一类动物，它们消化后的食物残渣排出的部位是（　　）

    When Jason's parents saw him for the first time, they were shocked（震惊）.This lovely little baby with shining blue eyes and curly hair was born disabled（残疾的）. But soon the young couple accepted this fact: Jason's arms are just half without hands and his legs aren't fully grown either. They even forgot to think of him as disabled.

    At the age of six, he told his mother he wanted to get down from the prosthetics（假肢）and play with other kids. This was the last time Jason had worn them. He now has an electric wheelchair（轮椅）, but he never uses it at home or when it is easy for him to move using only his body.

    Jason learned handwriting and coloring at school, holding the pen between the ends of his arms. He also learned to eat with forks at home. When he was ten, he fell in love with football. He never had a pair of shoes in his life because of the shape of his feet. He only wore socks on the football field. He never won a match, but he refused to give up. His strong arms and body, as well as some fantastic ways made him a respected（受尊重的）player on the school team. He went to a famous university after high school.

    Now Jason still faces many hardships in life, but he will make you believe that you can do what he has done. “Never be afraid of any difficulty”, Jason often encourages others in his speeches.

一株白菜就是一个植物体，白菜苗的结构层次可以描述为（　　）