Read this out loud!
- This is this cat.
- This is is cat.
- This is how cat.
- This is to cat.
- This is keep cat.
- This is an cat.
- This is idiot cat.
- This is busy cat.
- This is for cat.
- This is forty cat.
- This is seconds cat.
Now go back and read the third word only in each line from the start. ;-)