把分式$\frac{x+y}{x-3y}$中的x和y都扩大为原来的2倍，则分式的值（　　）

    I'm the mother of a fourteen-year-old. I have a rule for my daughter: be among the top 5 students or get punished in one way or another. She has been doing very well in school, but some friends of mine keep telling me that I put too much pressure on her. Am I wrong?

写作要点：

1)表明自己的看法；

2陈述自己的理由(可举例说明)；

3)提出至少两条建议。

要求：1)短文词数100左右。

2)内容充实，结构完整，语意连贯。

Hi, TigerMom,

    What puzzles you is actually a puzzle for many parents in China. My idea is



                                                                                                                                                                                                 Yours
                                                                                                                                                                                                  LiHua

若已知X、Y、Z、W四种金属与化合物之间存在化学反应有：① Y + ZCl₂ = Z + YCl₂、② X + ZCl₂=Z+ XCl₂、③ Y + 2HCl=YCl₂ + H₂↑、④W + YCl₂=W Cl₂ + Y；又知X与稀盐酸不能发生反应。试推断X、Y、Z三种金属的活动性由强到弱的顺序是  （　）               

如图所示为两个同心闭合线圈的俯视图，若内线圈中通有图示的电流I₁，则当I₁增大时关于外线圈中的感应电流I₂的方向及I₂受到的安培力F的方向，下列判断正确的是（   ）