选出下列各句中没有语病的一项（      ）

    “Happiness is not so much in having as sharing. We make a living by what we get, but we make a life by what we give. This website wouldn't exist(存在) without your contributions(贡献). Thank you!”

    The following files(文件) were upoload(上传) by teachers and language experts(专家). We thank them for contributing to the development of this website. If you decide to submit(提交) a file, please consider the following points:

    ♢First, you must register and log in.

    ♢Upload only EFL and ESL files:lesson plan, quizzes,tests…

    ♢Fill all the filed carefully. Provide a title and a description.

    ♢Only 200 kilobytes are allowed.

    ♢Examples of allowed file extensions are 'doc', 'pdf', 'ppt', 'docx', 'docm', 'pps', 'ppts'

    ♢Upload files will await moderation before publication.

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（   ）

如图，已知四个点A、B、C、D，根据下列要求画图：

（1）画线段AB； 

（2）画∠CDB；

（3）找一点P，使P既在直线AD上，又在直线BC上．