Na een bevestigende zin (+) is de zin ontkennend (-).
Na een ontkennende zin (-) is de zin bevestigend (+).
To be + hulpwerkwoorden (bv. have, can and could):
You are (+) at work today, aren't (-) you?
Your mother hasn't (-) met him before, has (+) she?
They can (+) make the exercises, can't (-) they?