题目内容：

    Imagine you are on a long car trip. It is night and you take a wrong turn onto a dark country road. With a sinking feeling, you realize that you have no idea where you are.

1., and the answer is written in light. A shining compass face, with north, south, east and west at the four points, and a big needle are pointing at north. What a relief! You turn your car around and head in the right direction guided by the sky.

For migrating birds, finding their way over long distances through the darkest nights is their second nature. 2. — directions written by light and magnetism (磁力). Some birds journey thousands of miles in their twice-yearly journeys. 3., like mountain ranges and rivers, to help decide the directions; but birds may also navigate using the stars, and by sensing — or even “seeing” — the Earth’s invisible magnetic field.

For many years, scientists have been studying what’s behind the strong ability of migrating birds to find their way to their winter and summer homes. Here is one thing that they agree on. 4.. This compass leads them to make their very first autumn flight in the direction that has been long-travelled by the rest of their species. 5..

A.Then you glance up at the sky

B.So birds are born knowing which way home is

C.They do it in part by reading directions in the sky

D.Magnetism is important for all animals, especially birds and fishes

E.When they’re on the way, they take the advantage of familiar landmarks

F.Migratory baby birds are already equipped with a kind of present inner compass

G.In birds, migration means two-way journeys — onward journey and backward journey