D．It was easier for plants to grow.

　　5．It can be inferred from the text that ______.

　　A．after the "Big Bang"，what the dust was to become remained a mystery

　　B．plants appeared before the animals

　　C．the plants multiplied and filled the oceans with oxygen

　　D．plants played an important part in the appearance of the animals

　　二、阅读课文"HOW LIFE BEGAN ON THE EARTH"，根据文章段落内容连线

　　1．Para．1　　 A．The formation（形成）of the earth.

　　2．Para．2 B．The importance of water for life.

　　3．Para．3 C．A widely accepted theory about the formation of the universe.

　　4．Para．4 D．The arrival of humans and their impact（冲击）on the earth.

　　5．Para．5 E．The development of plants and animals on the earth.