已知倾斜角为$45°$的直线l过椭圆$\frac{x^2}{4}+y^2=1$的右焦点，则l被椭圆所截的弦长是 （   ）

①下列有机物属于芳香烃的是____（填字母）．

②下列有机物属于羧酸类的是____（填字母）．

a． CH₃CHO        b． c．

③下列有机物属于糖类的是____（填字母）．

a．油脂        b．纤维素   c．蛋白质．

书面表达

假如你是某英语杂志社编辑王林，根据下面中学生小明的来信，给他写一封回信，解答他的困惑。

要求：1. 观点鲜明，结构合理，内容连贯；

2. 词数80左右，信的开头和落款已给出，不计入总词数。

Dear editor,

   Nowadays, many junior high school students are completely getting relaxed from busy study after graduation,  so what they would like to do most is to throw books away, hang out with friends at daytime and stay up late at night playing computer games or watching TV. What's your opinion about this? I'm looking forward to your reply.

                                                                                                                                                                                                      Yours sincerely

         Xiaoming

Dear Xiaoming，

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_____________________________________________________________________________________________________________________________________________________ ______________________________________________________________________________________________________________________________________________________

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Yours,

Wang Lin

如图是实验室制取纯净、干燥的二氧化碳气体，并探究其某些性质的实验装置．据图回答下列问题：

已知a＞b＞0，椭圆C₁的方程为$\frac{x^2}{a^2}+\frac{y^2}{b^2}=1$，双曲线C₂的方程为$\frac{x^2}{a^2}-\frac{y^2}{b^2}=1$，C₁与C₂的离心率之积为$\frac{\sqrt{3}}{2}$，则C₂的渐近线方程为（　　）