He found it hard for Alan to focus on his teachers for longer than five minutes, _________ if the lecture was boring. 

 When they knew there was a panda in the zoo, the children could ___ wait to see it.

The meeting was long and the speakers said ______nothing worth listening to.

Lily has been in love with Tom ___ since she met him last year.

I think you’ve got to the point where a change is needed , _____, you’ll fail .