动词填空 用括号内所给动词的适当形式填空。
⑴Mom makes me eat an apple a day ____  (keep) the doctor away.
⑵She spent as much time as she could ____  (explain) it to us, but we still didn’t believe her.
⑶I was told that some students in Grade Seven and Eight ____  (take) part in an English camp in
Australia the next month.
⑷I remember his brother ____  always ____ (ask) questions in class when he was at the primary school.
⑸The various fantastic drawings the famous artist devoted himself to ____  (show) in our school hall the day before yesterday.
⑹The girl sitting next to me on the plane was nervous, for she____  never ____  (fly) before.
⑺The number of deaths from heart disease____  (reduce) greatly if people eat more fruits and vegetables.
⑻“So Young”, a new movie directed by Zhao Wei, ____ (earn) about 600 million yuan in the last few weeks.

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．

如图所示，一个质量为m的物体从高为h的曲面上一点A处，由静止开始下滑，滑到水平面上B点处停止．若再用平行于接触面的力将该物体从B处拉回到原出发点A处，则需要对物体做功的最小值为（   ）