ANSWER:
6.Unless you promise to try harder, I'll help you.
7.If someone has a key, we can get into the house.
8.Unless we do not try to reduce it, the world population won't continue to rise.
9.Unless you keep your feet dry, you won't catch a cold.
10.Unless there is water, This tree will grow.
11.Should you close the window, the room will not be cold.
12.Should he is free, he will come to visit me.
13.Were she to eat too much, She would be overweight.
14.Were Peter late, he would be punished.
15.Should he will catch the first bus, he will come on time.
16.If I know her email address, I can tell you.
17.If I didn't feel tired, I can play football this afternoon.
18.If she doesn't work in the morning, she will have time to watch TV.
19.Were he to have a watch, he's never late for work.
20.Were I tall, I can join the basketball team.
21.If his watch wasn't 5 minutes slow, Jack wouldn't late for the party.
22.Had Sam know the highway was closed, he took another.
23.Unless I didn't lose my key, I didn't have to wait for my roommate
24.If we didn't go to bed late last night, we aren't tired today.
25.If I knew you were in the hospital, I would visit you.