1.Unless you (tell)_____tell_______the truth,I won't help you. 
2.You'll get pneumonia if you (not change)_____don't change_____your
wet clothes.
3.If I had known that you couldn't eat  octopus,I (not buy)______wouldn’t have bought______it.
4.Dan (arrive)____arrived_____safe if he drove slowly.
5.I (not buy) ____didn't buy_____things on the installment system if I were you.
 

1/ Tell
2/ don’t change
3/  wouldn’t have bought
4/  hung
5/ would be