He goes up quickly and bits the fox's

意思是：它（乌龟）迅速过来咬住狐狸的尾巴.
原故事是这样的：
A hungry fox is looking for something to eat .He sees a frog (青蛙) playing near the river ,He goes up to the frog and is going to eat it .
Just at that time a tortoise (乌龟) comes up and sees all this .He goes up quickly and bits(咬) the fox's tail (尾巴).The fox can't move and the frog jumps into the river."I' m going to throw you into the sky." says the fox angrily to the tortoise." Thank you.I'm always hoping to go into the sky," says the tortoise."I'm going to throw you into the fire" says the fox again to the tortoise." Thank you very much.I'm very cold and want to keep warm," the tortoise says."Don't throw me into the river .I'm afraid of water very much," says the tortoise in tears.When he hears this,the fox gets up and throws the tortoise into the river.Now the tortoise is swimming in the river happily and laughing at the fox.