Question

At, call, try, discover, however, beyond, travel, send, be, understand, reach， good

Scientists think that there has    1    life on the earth for millions of years.    2   , we haven’t found life on other planets yet. Why?

The earth is a planet and it goes around the sun. There are other planets that also go around the sun. The sun and its planets    3    the solar system(太阳系). The solar system is a small part of our galaxy(银河系).

The stars we see at night are the suns in other solar systems. There are more than 200 billion stars in our galaxy, the Milky Way, and our sun is only one of them.

But scientists have    4    many other galaxies in the universe. They are a long way away and their light has    5    for many years to    6    us. It’s hard to    7    how large the universe is.

Scientists have    8    lots of spacecrafts to visit other planets in our solar system, and some spacecrafts have gone    9    the solar system. However, no one has discovered any life in space yet.

But why has no one from other planets sent us a message? Have they   10   to send information to us? Are we alone. Is there life out there in space? We don’t know.

1.___________  2.____________  3.____________  4.______________  5.______________

6.___________  7.____________  8.____________  9.______________ 10.______________

Answer 1