喜欢冒险的乐乐利用假期进行了一次骑行之旅（见下图）。旅行时，乐乐看到沿途的自然景观自东向西大致呈现由草原向荒漠草原、荒漠变化。影响这些自然景观变化的主要因素是（    ）

    There was once a lonely girl who wanted to get love. One day when she was ____ in the woods she found two hungry birds. She took them____and put them in a small cage. She looked after them with love and the birds grew strong. Every morning, they greeted her with____wonderful song. The girl loved them very much.

    One day the girl left the cage door____ One bird flew from the cage. The girl was afraid that he would fly away. As he flew close, she caught him wildly. She was very happy____him. Suddenly she felt the bird unable to walk. She opened her hand____was surprised to find the bird was dead. Her love ____ him.

    She noticed the other bird jumping up and down in the cage. She could feel his great____for freedom. She lifted him from the cage and let him fly into the air. She wanted the bird to be happy. The bird circled once, ____, three times. Finally, he flew closer and landed softly on her shoulder. He sang the ____ music that she had ever heard.

造成地球上海陆变迁的主要原因是   

有三个自然数，甲数与乙数的比是3：5，乙数与丙数的比是2：5，甲、乙两个数的和是80，则乙数是____，丙数是____。