根据短文理解，从A、B、C三个选项中选择最佳答案填空。

    Jimmy is an English boy. He wants to have a friend in China. He likes 1 very much. It's relaxing for him. He plays sports 2 his classmates after class. He has five soccer balls, two 3 and one basketball. But he doesn't like tennis. He thinks it's 4. 

Jimmy has a healthy eating 5. He likes fruit and vegetables. 6 are his favorite (最喜欢的) vegetables. He often (经常) has fruit salad 7 dinner. He doesn't eat 8 or ice-cream. He doesn't want to be 9. 

    Do you like him? Do you 10 to be his friend? You can e-mail him at jimmy 012@ yahoo.cn.

如图，在△ABC中，∠C=90°，AC=BC=4，D是AB的中点，点E、F分别在AC、BC边上运动（点E不与点A、C重合），且保持AE=CF，连接DE、DF、EF，在此运动变化的过程中，有下列结论：

①∠DEF是等腰直角三角形；②四边形CEDF不可能为正方形；

③四边形CEDF的面积随点E位置的改变而发生改变；

④点C到线段EF的最大距离为 $\sqrt{2}$ ．

其中正确结论的个数是（    ）

据唐代天宝年间统计的全国户口数字，秦岭、淮河以南地区的户数占45.5%，以北占到54.5%；据北宋《太平寰宇记》所载北宋初期全国户数，秦岭、淮河以南地区的户数占59.1%，以北则为40.9%。这一变化（   ）

读图，完成下列各题．