题目内容：

Is there intelligent 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. They believe intelligent life exists (存在) somewhere in the universe. They also think we will soon contact these beings.

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 Barnet. 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 Milk 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 signs. 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.”

1.Seth Shostak and Alexandra Barnett are _______________.

A. astronomers.   B. farmers    C. singers    D. drivers

2.What is the best title for Paragraph Two?

A. The Age and Size of Earth

B. Our Galaxy： The Milk Way

C. Why Intelligent Life Might Exist

D. Earth： The Only Planet With Intelligent Life

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 Milk Way didn’t exist at that time.

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

A. They are 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 signs.

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

A. Messages.               B. Tools.

C. Intelligent beings.     D. Radio signs.