如图所示，在水平地面上固定一倾角θ=30°、表面光滑的斜面体，物体A以v₁=5m/s的初速度沿斜面上滑，同时在物体A的正上方，有一物体B以某一初速度水平抛出，如果当A上滑到最高点时恰好被B物体击中．（A、B均可看做质点，重力加速度g取10m/s²） 求：

    小城里每一个庭院都栽了很多树。有桉树、椰子树、橄榄树、凤凰树，还有别的许多亚热带树木。初夏，桉树叶子散发出来的香味，飘得满街满院都是。凤凰树开了花，开得那么热闹，小城好像笼罩在一片片红云中。

    小城的公园更美。这里栽着许许多多榕树。一棵棵榕树就像一顶顶撑开的绿绒大伞，树叶密不透风，可以遮太阳，挡风雨。树下摆着石凳，每逢休息的日子，石凳上总是坐满了人。

根据短文理解，选择正确答案。

    A year ago, I paid no attention to English idioms( 习语 ), though my teacher emphasized(强调) the importance again and again. But soon, the importance of English idioms was shown in an amusing experience.

    One day, I happened to meet an Englishman on the road, and soon we began to talk. As I was talking about how I was studying English, the foreigner seemed to be astonished. Gently shaking his head, shrugging his shoulders, he said, “You don't say!” “You don't say!” I was puzzled. I thought, perhaps this is not an appropriate(合适的) topic. “Well, I'd better change the topic.” So I said to him. “Well, shall we talk about the Great Wall? By the way, have you ever been there?” “Certainly, everyone back home will laugh at me if I leave China without seeing it. It was magnificent(宏伟的).” He was deep in thought when I began to talk like a tourist guide. “The Great Wall is one of the wonders in the world. We are very proud of it.” Soon I was interrupted again by his words “You don't say!” I couldn't help asking, “Why do you ask me not to talk about it?” “Well, I didn't request you to do so,” he answered, greatly surprised. I said, “Didn't you say ‘you don't say?'” Hearing this, the Englishman laughed to tears. He began to explain, “‘You don't say' actually means ‘really!'. It is an expression of surprise. Perhaps you don't pay attention to English idioms.” Only then did I know I had made a fool of myself. Since then I have been more careful with idiomatic expressions(习语表达). Remember -- what the English teachers said is always right to us students.