Once upon a time，a hippo（河马）lived in a river next to a big tree．

One day，a bird came and nested （筑巢）in the tree．The songs of the bird filled the hippo with so much envy（羡慕）that he couldn't think of anything else．Every day he would think why he wasn't born to be a bird even though the bird told him many times he was so lucky to be so big and such a good swimmer．

Finally，the hippo made up his mind that he would come out of the river，climb the tree and start singing．However，when he tried to climb the tree，it was very clear that the hippo didn't have wings to fly，or claws to climb with．

Realizing that he would never climb up the tree，he angrily hit the tree until it came crashing to the ground．Then he stepped onto the leaves of the fallen tree，and began singing．

Unfortunately，hippos can't sing，either．All that came from his mouth were terrible noises，and when the other animals heard this，they all came around to make fun of the hippo．

He was so ashamed by this．He also felt bad about having knocked the tree over．He used all his strength to raise the tree back up again，and look after it until it completely recovered（康复）．

Complete the summary of the passage above with one word for each blank.

Once upon a time，there was a hippo living in a river next to a big tree.He （1） 　 　the bird's singing.He wondered why he wasn't （2） 　     　in singing songs.

Finally，the hippo （3） 　     to come out of the river，climb the tree and start singing.Unluckily，he （4） 　    　to climb the tree.He was so angry that he hit the tree until it fell over.Then he began to sing on the leaves of the fallen tree.But he couldn't sing，either.Other animals came to （5） 　     　at him because of his terrible noises.

At last，he felt ashamed to knock the tree over.He tried to help the tree recover.