阅读下列解题过程，然后解题：

题目：已知$\frac{x}{a-b}=\frac{y}{b-c}=\frac{z}{c-a}$（a、b、c互不相等），求x+y+z的值．

解：设$\frac{x}{a-b}=\frac{y}{b-c}=\frac{z}{c-a}=k$，则x=k（a﹣b），y=k（b﹣c），z=k（c﹣a），

∴x+y+z=k（a﹣b+b﹣c+c﹣a）=k•0=0，∴x+y+z=0．

依照上述方法解答下列问题：

已知：$\frac{y+z}{x}=\frac{z+x}{y}=\frac{x+y}{z}$，其中x+y+z≠0，求$\frac{x+y-z}{x+y+z}$的值．

根据短文理解，完成各题任务。
C
    Sally is an English girl. She is my English teacher, Mrs. Brown's daughter. She is only five years old. (A)She can't go to school. She likes playing ping-pong.
    Her favorite ping-pong player is Zhang Yining. Sally is in the ping-pong club. She goes to the ping-pong club every day. She plays ping-pong for two hours there.
    Sally has a sister. Her name is Maria. She is in our class. She likes running. She runs with her mother every morning. (B)她最喜欢的赛跑明星是刘翔. Maria says she wants to be a running star like Liu Xiang.

You only need to pay for breakfast and dinner.   

如图，AB∥CD，BC∥DE，若∠B=40°，则∠D的度数是（　　）

在柠檬中插入两种不同的金属可以制得水果电池。相同条件下，水果电池的电压与两种金属的活动性差异大小有关。下列柠檬电池的两种金属，活动性差异最大的是（  ）