please turn on bbc1. we want to watch a documentary about australia. if you turn on bbc1, we'll watch a documentary about australia.
you won't be able to read that book if you don't borrow it from the school library. if you don't borrow the book from the school library, you won't be able to read it.
don't come back home too late from the disco. you'll be too tired the following morning. if you come back home too late from the disco, you'll be too tired the following morning.
the students will go to new york during the summer. in that case, they will improve their english. if the students go to new york during the summer, they'll improve their english.
they won't let you into that pub if you aren't 18. if you aren't 18, they won't let you into that pub / are 18, they'll let you into that pub.
people eat lots of fruit and vegetables. in that case, they get very healthy. people get very healthy if they eat lots of fruit and vegetables.