语法填空「20巧.吉林省吉林市第一中学高一下学期第二次质检]

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   How life began on the earth 

    How the earth came into existence and how life began on the earth, no one knows 1.________  (exact) , as it happened so long ago. However, according to a widely 2. ________  (accept) theory, the universe began with a "Big Bang" that threw matter 3. _________  all directions.  After that, atoms began to form and combine to create stars and other bodies. Between 4. 5 and 3. 8 billion years ago, the earth became 4. ____  violent that it exploded loudly with fire and rock, producing water vapour and other gases.

   When the earth cooled down, water appeared on its surface. Water had also appeared on other planets like Mars but, 5. ______  (like) the earth, it had disappeared later. It was not immediately obvious 6. ______ water was to be fundamental to the 7. _______ (develop) of life. What many scientists believe is that the continued presence of water allowed the earth 8. ______ (dissolve) harmful gases and acids into the oceans and seas. This produced a chain reaction, which made 9. ________  possible for life to develop.

Millions of years later, life began to develop on the earth, from simple forms to advance ones, from oceans to land, from plants to animals. Finally about 2. 6 million years ago some clever animals appeared. 10.______ they have, in their turn, become the most important animals on the planet.

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