I . 完形填空 The year is 2094. It has been announced that comet ( 彗星 ) is heading towards the Earth. Most of it will miss our planet, but two pieces will probably 1 the southern half of the Earth. On 17 July, a 2 which is four kilometers wide enters the Earth's 3 with a massive explosion. About half of the piece is destroyed, but the 4 part hits the South Atlantic at 200 times the speed of 5 . The sea 6 and a huge hole is made in the sea bed. Huge waves are created and spread out from the hole. The wall of water, a kilometer high, rushes towards southern Africa at 800 kilometers an hour. Cities on the African coast are totally destroyed and millions of people are 7 . Before the waves reach South America, the second piece of the comet 8 in Argentina. Earthquakes and volcanoes are 9 off in the Andes Mountains. The shock 10 move north into California and all around the Pacific Ocean. The cities of Los Angeles, San Francisco and Tokyo are completely 11 by earthquakes. Millions of people in the 12 half of the earth are already dead, and the 13 won't be safe for long. Because of the explosions, the sun is 14 by clouds of dust, and temperatures around the world fall to almost zero. Crops are ruined. The sun won't be seen again for many years. Wars 15 as countries fight for 16 . A year later, no more than 10 million people remain 17 . Could it really 18 ? In fact, it has already happened more than once in the history of the Earth. Science shows that dinosaurs ( 恐龙 ) 19 on the Earth for over 160 million years. Then 65 million years ago they suddenly disappeared. Many scientists believe that the Earth was hit by a piece of heavenly object. The dinosaurs couldn't live through the cold 20 that followed and they died out. Will we meet the same end?