126.We can only get into the house if someone has a key.
127.If it doesn't stop raining,we won't go out.
128.Water couldn't run down hill if it wasn't graviated.
129.If I hadn't studied hard,I wouldn't have passed the final examination.
120.If you don't listen to the teacher's explanation,you can't understand anything.
121.If I hadn't been sick yesterday,I would have gone to class.
122.If Alan ate breakfast,he wouldn't always overeat at lunch.
