第一部分 阅读理解(共两节，满分40分)
第一节(共15小题；每小题2分，满分30分)
阅读下列短文，从每题所给的四个选项(A、B、C和D)中，选出最佳选项。
A
The sea is home to billions of plants and animals.Many live only near the sunlit surface.Oceanographers classify marine living beings by separating them into two main groups: plants and animals.
