I think he’s been drinking, _________ I’m not quite sure.
You may go fishing if your work _______.
Follow your teacher’s advice, _______ you’ll make great progress in your English.
You _______ write the poem down. Our teacher will give us a copy.
Knowing how to _______ a map can help you when you are travelling in a strange place.
Now the air in our city is _______ than it used to be. Something must be done to stop it.