若椭圆$C_1:\frac{x^2}{a_1^2}+\frac{y^2}{b_1^2}=1(a_1>b_1>0)$和椭圆$C_2:\frac{x^2}{a_2^2}+\frac{y^2}{b_2^2}=1(a_2>b_2>0)$的焦点相同且a₁>a₂.给出如下四个结论：
①椭圆C₁和椭圆C₂一定没有公共点；          ②$\frac{a_1}{a_2}>\frac{b_1}{b_2}$；
③$a_1^2-a_2^2=b_1^2-b_2^2$；                ④$a_1-a_2<b_1-b_2$.
其中，所有正确结论的序号是（   ）

在一个装满水的容器中，放入一质量为20g的物块，从容器中溢出15g的水，则该物块在水中的浮沉情况和水对容器底部的压强应该是（　　）

阅读下面材料， 在空白处填入适当的内容（1个单词）或括号内单词的正确形式。

    Jenny began to go to school when she was at the age of six. She liked her ____ (one) day very much. Her teacher, Miss Black, ____ (be) very nice, too.

    At the end of the second day, the other children ____ (leave) the classroom after school but Jenny stayed behind and waited. At first, Miss Black had some work to do and ____ (not) see Jenny, but then she looked up and saw her.

    "Why not go with the ____ (other), Jenny?" she asked her kindly. "Do you want ____ (ask) me any questions?"

    "Yes. Miss Black," Jenny said.

    "____ is it?" Miss Black asked.

    "What did I do in school today?" Jenny said.

    Miss Black laughed. "What did you do in school today?" she said. "Why did you ask ____ (I) that, Jenny?"

    "____ I'm going home now," Jenny answered, "and my mother ____ (would) ask me."