1 . There will be a shortage of water unless it rains .
If it doesn't rain, there will be a shortage of water.
2 . Unless you study harder , you won't pass the final exam .
If you study harder, you will pass the final exam.
3 . Unless this biodiversity were maintained, marine life would be at stake .
If this biodiversity weren't maintained, marine life would be at stake.
4 . My teacher speaks too quickly . I can't understand her explanation .
If my teacher spoke more slowly, I could understand her explanation.
 5 . I drink too much strong coffee, that's why I can't sleep .
If I drank less strong coffee, I could sleep.
6 . The weather is not fine , that's why I can't sleep .
If the weather was fine, I could sleep.
7 . They felt tired because the meeting was long .
If the meeting had been shorter, they wouldn't have felt tired.
8 . He couldn't do that exercise because he didn't learn his lesson carefully 
If he had learnt his lesson carefully, He could have done that exercise.
9 . John was ill , so he didn't go to the party .
If John had been fine, he could have gone to the party.
10 . I don't know Mai's address , so I can't come to see her .
If I knew Mai's address, I could come to see her.
11 . If she doesn't come here immediately , I will omit her name out of list 
Unless she comes here immediately , I will omit her name out of list.