I hold the string in my hand.
I drag the string on the ground.
Then I run as fast as I can.
The kitten tries to catch the string with her paw.
Sometimes she catches the string.
Then she puts it into her mouth and runs away.
Sometimes, when she runs after me, she stumbles and falls.
The kitten can not always get the string.
Sometimes I run too fast for her.
Then she can not catch the string.