the first four planets重点内容

Is there intelligent (有智力的) life on other planets? For years, scientists said “no.” or “we don’t know.” But today this is changing. Seth Shostak and Alexandra Barnett are astronomers(天文学家). They believe intelligent life exists (存在) somewhere in the universe. They also think we sill soon contact these beings(人；生物).
Why do Shostak and Barnett think intelligent life exists on other planets? The first reason is time. Scientists believe the universe is about 12 billion years old. “This is long enough for other planets to have intelligent life,” say Shostak and Barnett. The second reason is size—the universe is huge. “Tools like the Hubble Telescope(哈勃望远镜) have shown that there are at least 100 billion galaxies,” says Shostak. “And our galaxy, the Milky Way, has at least 100 billion stars. Some planets going around these stars might be similar to Earth.”
In the past, it was hard to look for signs of intelligent life in the universe. But now, powerful telescopes(高倍望远镜) allow scientists to discover smaller planets—the size of Mars or Earth—in other solar systems. These planets might have intelligent life.
Have beings from space already visited Earth? “Probably not,” says Shostak. “It’s a long way away. However, intelligent beings may contact us in other way, such as radio signals(信号). In fact, they may be trying to communicate with us now, but we don’t have the right tools to receive their messages. However, this is changing. By 2025, we could make contact with other life forms in our universe and we might help each other.”
小题1:Seth Shostak and Alexandra Barnett are _____.

A．astronomers

B．farmers

C．singers

D．drivers

小题2:What is the best title for Paragraph 2?

A．The Age and Size of Earth

B．Our Galaxy: The Milky Way

C．Why Intelligent Life Might Exist

D．Earth: The Only Planet with Intelligent Life

小题3:Why was it hard to look for signs of intelligent life in the universe in the past?

A．There were not any smaller planets.

B．There were not any powerful telescopes.

C．The astronomers were not interested in them.

D．The Milky Way didn’t exist at that time,

小题4:Why haven’t beings from space visited us yet according to Shostak?

A．They’re afraid of us.

B．It’s a long way away.

C．They don’t want to see us.

D．They don’t know how to use radio signals.

小题5:What does the underlined phrase “life forms” in the last paragraph mean?

A．Messages

B．Tools

C．Intelligent beings

D．Radio signals

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.
小题1:What is this passage mostly about?

A．Comets and the sun.

B．Why comets are like snowballs.

C．Who discovered the first comet.

D．Facts about comets.

小题2:How does the writer help the reader understand what a comet looks like?

A．By telling about a famous one.

B．By explaining how far away it is.

C．By describing how fast it moves.

D．By describing it as a dirty snowball.

小题3:What is the most likely reason the writer wrote this passage?

A．To give information about comets.

B．To tell readers about famous comets.

C．To explain the importance of comets.

D．To encourage readers to look for comets.