Water is the "life blood" of our earth. It is in every living thing. It is in the air. It runs through mountains and valleys. It forms lakes and seas. Nature has a great water system（系统）.Rainwater finds its way to rivers and lakes. River water runs into the sea. At the mouths of the rivers, fresh water joins the salt water of the sea.
Here at the mouth of a river there is much important plant and animal life. But pollution destroys this life. We have to clean our rivers. Man has to work with nature, not against it.
【小题1】Water is like________.
【小题2】________ is in every living thing.
【小题3】The mouth of a river is near _________.
| A．the sea | B．a lake | C．a mountain |
【小题4】There is much plant and animal life at the _________ of a river.
【小题5】We have to ________ our rivers.
