Step 1 Choose the best answers according to the passage on P64.
1．Where does the passage probably come from?
A．A newspaper article.
B．A scientific report.
C．A school science textbook.
D．A collection of photographs.
2．Which of the following is the best summary of the passage?
A．Using the CassiniHuygens space probe, an international space project has proved that Saturn is light enough to float on water, and that one of its moons, Titan, has liquid on the surface like the Earth.
B．Titan and Phoebe are two of Saturn's moons, and are made of a mixture of tiny pieces of rock, water and frozen gases. They look very much like the Earth and our Moon. The photos taken by the space probe are so clear that it is easy to forget how far they come.
C．The CassiniHuygens space probe, which was launched in 1997 to explore Saturn, has sent back photos of the planet and its moons from a distance of oneandahalfbillion kilometres.
答案：1～2 AC
