20、Many years ago，there were lots of trees on earth，because summer lasted a whole year．What was the forest like? It is not difficult to see，because parts of that ancient（古老的）forest still stand．It is the rainforest．Here，even in a sunny day water drops through the leaves．

Today's largest rainforest is in South America．It covers about a million square miles．All the trees are very tall；the young trees are nearly sixty feet high．But it is not easy for some to grow higher because very little sunlight leaches them．

Many trees are about 60 to 120 feet high．Some are even taller．The tallest trees can be 200 feet high．

In this forest of tall trees，plant life is rich，animal life is rich，too．At different heights live different animals and many different noises can let you know where they are．

根据短文内容，选择最佳答案。

1．There were lots of trees on earth many years ago because of the _________．

A．cold weather          B．largest forest          C．warm weather               D．rainforest

2．A rainforest has enough _________．

A．trees                    B．rainfall（雨量）      C．forest                    D．leaves

3．There is rainforest _________．

A．only in South America                              B．only in the old days

C．in some parts of the world                          D．below the sea

4．Young trees share little sunlight because _________．

A．tall trees are above them                           B．there isn't enough sunlight

C．they needn't much sunlight                          D．it is summer the whole year

5．You can always find different animals by _________．

A．their colors                                             B．the noises they make

C．climbing the trees                                       D．watching them carefully