根据短文内容及首字母提示完成短文。

     Round eyes, round head, round ears, round body! What is this lovely little animal? He looks  _ 1__ 

a bear. But he is not a bear. He is a KOALA(考拉).  

     People in Australia love koalas and take care of t _ 2 _ .They have set up places for koalas to live s  3  . No one can kill them for their pretty fur. When a koala is b _ 4_  ,he has no fur. And he is not as

big as your

little toe! The mother koala has a pocket in the front of her b   5      .The baby goes into this warm

pocket. There he stays for six m    6     .  

     The koala could not live w    7   a special kind of tree. The tree gives him both his home and his

food.For most of the day the koala s    8   in the tree. At night the koala looks for food. He may go

miles to find it.  He likes eating only the bark (树皮) and the   9   of the trees. He eats n    10  else.

And he eats more than two pounds each night!   How lovely the koalas really are!

电机车换向磁极是用以（）。

A.电机的换向

B.减弱电机旋转时换向器上产生的换向火花

C.增加电机的牵引力

D.减少电机电流