There are many natural mysteries and wonders in the world，here are some of them.
   Fossil（化石）footprints
   About 11，000 years ago，some ancient humans went for a muddy walk in Africa.They left more than 400 footprints，which became fossils.It's the largest collection of ancient African footprints ever found.Scientists have studied all the footprints.And they have learned more about the people who left them.All of the footprints came from feet.Scientists found the footprints of 17 people who probably walked togejye.air.The footprints were all traveling in the same direction and at the same speed.From the size of the footprints，scientists think the group was mostly adult women.They may have been out gathering food together.
   Snakes stick together
   Can snakes be friends？Some scientists recently found the answer by closely watching 40 young garter snakes.These small，harmless snakes are common in North America.Scientists divided the snakes into 10 groups.Then they put each group into a small space together for eight days.They found that snakes do seem to have friends.Each snake liked to stay together with certain snakes more than others.Even when scientists moved them around，the snakes often went back to their same friends.Snakes are known for being unfriendly--but it's not always true，scientists say.
   How koalas get water
   All living things need water.But they get it in different ways.You drink water from a glass.Plants take it in with their roots （根）Koalas get water from eucalyptus （桉樹）leaves they eat.But scientists have discovered that koalas have another way to get water：They lick （舔）trees.People noticed the surprising behavior while watching wild koalas in Australia.During rainstorms or right after，rainwater dropped down from tree trunks.Some koalas got the running water while they sat in the trees.One koala was so thirsty that it kept licking a wet tree trunk for more than 30 minutes without stopping.

（1）What is the structure of this passage？

B

B

A．

B．

C．

（2）Who left the fossil footprints？

A

A

A．Women.
B．Koalas.
C．Scientists.
（3）What will happen if people move snakes around？

C

C

A．They will fight with each other.
B．They will move away quickly.
C．They will go back to other snakes.
（4）How do koalas mainly get water？

C

C

A．From the lakes and rivers.
B．From the roots and trunks.
C．From the leaves and rain drops.