语法填空（共10小题；每小题1.5分，满分15分）
阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空。
The earth is a special planet in the solar system. The explosion of the earth produced carbon, nitrogen, vapor and other gases,    1   (make) the earth’s atmosphere. As the earth cooled    2  , water which is fundamental    3   the development of life appeared and stayed on the surface. The continued    4  (present) of water allowed the earth to dissolve harmful gases into the oceans and this produced a chain reaction which made    5   . possible for life to develop.
Many millions of years later, the arrival of small plants encouraged the development of early shellfish    6   all sorts of fish. Then, with the first green plants appearing on land, land animals appeared and dinosaurs developed and existed on the earth for millions of years. Then Dinosaurs’ sudden disappearance made the rise of mammals possible on the earth. They were different from all life forms    7   ever existed in the past because they produced young from within their bodies. Finally, some small clever animals with hands and legs __8___(appear) and spread all over the earth. Thus they, in    9   turn, have become the most important animals. However, they are putting too much carbon dioxide into the atmosphere. So for millions of years to come,    10   life will continue on the earth will depend on whether the present problem can be solved.