请根据提示补写名句或填写课文原句。
①抽刀断水水更流，            。   

②             ，秋水共长天一色。
③蓦然回首，那人却在，         。  

④             ，不求闻达于诸侯。
⑤古诗词中许多诗句运用典故，抒情言志,言精意丰。李白《行路难》中“      ，       “，用姜尚（姜太公）和伊尹的典故，表达自己施展宏伟抱负的愿望；苏轼《江城子·密州出猎》中“      ，       ”，以魏尚自比，希望能得到朝廷的信任和重用，承担起卫国守边的重任。

给出了结论：

⑴二次函数y=ax²+bx+c有最小值，最小值为﹣3；

⑵当 {#mathml#}$-\frac{1}{2}<x<2${#/mathml#} 时，y＜0；

⑶二次函数y=ax²+bx+c的图象与x轴有两个交点，且它们分别在y轴两侧．则其中正确结论的个数是（   ）

研究性学习小组对碳酸钠和碳酸氢钠的性质进行探究，请你参与实验．

实验一：比较两种物质的热稳定性设计如右图装置：小试管套装在带有支管的大试管中，整套装置气密性好，其他装置略去．

Comets(彗星) are parts of our solar system. Like the planets, they go around the sun.
But comets are not made of solid rocks like planets. A comet is a ball of dust, stones, and ice. Many people call comets dirty snowballs.
The "snowball"may be only a few miles across. But when the sun heats the "snowball,"much of it is changed to gases. The gases spread out and form the comet's head, which may be thousands of miles across.
A comet moves fast in its trip around the sun. But when we see it, the comet does not seem to move. That's because it is so far away. The moon moves fast, but when you look at it, you can't see any motion(运动). That's because the moon is far away.
Each year astronomers(天文学家) discover new comets. Some of them are seen only once. They make one trip around the sun and then go away out into space. The sun's gravity cannot hold them.
Other comets, like Halley, keep returning. They have been captured by the sun. Halley's earliest visit was probably 3,000 years ago. It may keep returning for another 3,000 years.
But every time a comet goes around the sun, the comet loses part of itself. Gases and dust are pulled out of the comet. That's why Halley is now dimmer（暗淡的） than it used to be. Next time it visits us, in 2062, it may be even dimmer. Each visit it may get dimmer and dimmer, until it finally disappears.

下列式子是分式方程的是(     )

下列式子是分式方程的是(     )